Method and plant for producing iron from roasted pyrites

ABSTRACT

The invention relates to a method and a recovery system for obtaining/recovering metallic iron and/or iron compounds, in particular iron chloride, from ores and/or ore tailings, especially from pyrite tailings, preferably from roasted pyrites produced during sulphuric acid manufacture.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a National Stage filing of International ApplicationPCT/EP 2013/063129, filed Jun. 24, 2013, claiming priority to PCT/EP2013/001475 May 17, 2013, entitled “Method and Plant for Producing Ironfrom Roasted Pyrites”. The subject application claims priority to PCT/EP2013/063129, and to PCT/EP 2013/001475 and incorporates all by referenceherein, in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to the technical field of the extractionof metals, more particularly of iron, and/or of non-noble nonferrousmetals and/or noble metals from ores and/or ore residues, preferablyfrom pyrite residues or pyrite cinder, more particularly roastedpyrites.

The present invention relates more particularly to a method forobtaining/recovering metallic iron or iron compounds, more particularlyiron chloride, from ores and/or ore residues, preferably from pyriteresidues, more preferably from roasted pyrites obtained in theproduction of sulfuric acid.

Furthermore, the present invention relates to a corresponding recoveryplant, more particularly for obtaining/recovering metallic iron or ironcompounds, more particularly iron chloride, from ores and/or oreresidues, preferably from pyrite residues, very preferably from roastedpyrites obtained in the production of sulfuric acid, it being possiblefor the plant of the invention to be used to implement the method of theinvention.

The present invention accordingly also relates to the use of therecovery plant of the invention in the method according to the inventionfor obtaining/recovering metallic iron or iron compounds, moreparticularly iron chloride, from ores and/or ore residues.

In general, ores comprise, in particular, chemical compounds of metals,such as iron compounds, in the form of iron oxides, iron carbonates andiron sulfides, for example, it being possible for the metal compounds inquestion to be present in the ore as a mixture with nonferrous minerals.

The most important iron ores include magnetite, limonite, hematite andsiderite. While iron in the case of magnetite is in the form of iron(II, III) oxide (Fe₃O₄), iron in hematite is encountered fundamentallyas iron (II) oxide (Fe₂O₃). In siderite, furthermore, iron is primarilyin the form of iron (II) carbonate (FeCO₃).

Known additionally, however, are natural ores in which iron is presentprimarily in conjunction with sulfur. These include, in particular,pyrite, which on account of its metallic luster and its brassy yellowcoloring is also known synonymously as fool's gold.

In particular, pyrite includes a series of further technologicallyand/or economically significant metal components, such as zinc, copper,cobalt and lead, for example, and also further ingredients based oncalcium and silicon, which in general, as a result of the primaryindustrial utilization of pyrite for the purpose of producing sulfuricacid, are not valorized and hence remain, so to speak, unutilized in thematerial or resulting roasted pyrites.

As mentioned above, iron in pyrite is present in particular in the formof the sulfide, more particularly as iron (II) disulfide or FeS₂, inthis context, pyrite represents the most widespread sulfide mineral. Onan industrial scale, it is used as starting material for producing orobtaining sulfuric acid, with the resulting residues being referred toas pyrite cinder or, synonymously, as purple ore or roasted pyrites.

In the course of the production of sulfuric acid using pyrite asstarting material, the general procedure in the prior art is to subjectpyrite, as sulfidic metal ore, to roasting in the presence ofatmospheric oxygen, with iron sulfide present in pyrite giving risefirst of all to sulfur dioxide (SO₂) and to iron oxides in differentoxidation states. Subsequently, particularly as part of what is called acontact method or in a contact kiln, the resulting sulfur dioxide isoxidized using a catalyst, vanadium pentoxide, for example, and in thepresence of additional oxygen, to form sulfur trioxide (SO₃). Subsequentadsorption and/or reaction with water then produces sulfuric acid(H₂SO₄).

In summary, therefore, the production of sulfuric acid starting frompyrite is carried out in particular in the form of a four-stageoperation, the method comprising the following steps:

-   -   (i) roasting of pyrite, for example in a fluidized bed roasting        furnace, for obtaining sulfur dioxide starting from iron sulfide        or iron disulfide or iron (II) disulfide (with the corresponding        chemical reaction equation 4FeS₂+11O₂→2Fe₂O₃+8SO₂);    -   (ii) subsequent gas purification, particularly for purifying        sulfur dioxide obtained beforehand;    -   (iii) oxidation of sulfur dioxide to sulfur trioxide (with the        corresponding chemical reaction equation 2SO₂+O₂→2SO₃), a        reaction which can be carried out with the use of catalyst in a        contact reactor or tray reactor; and    -   (iv) adsorption of sulfur trioxide with hydrous sulfuric acid,        more particularly concentrated hydrous sulfuric acid, for the        purpose of obtaining further sulfuric acid, with the sulfur        trioxide acting as an anhydride of the resulting sulfuric acid        (with the chemical reaction equation SO₃+H₂SO₄(H₂O)→2H₂SO₄).

Generally speaking, on the industrial scale, sulfuric acid is employedin very large quantities and in numerous sectors of the chemicalindustry: a large proportion of the sulfuric acid produced goes into theproduction of fertilizers. Furthermore, sulfuric acid acts as a startingproduct or intermediate in the production of other industrially relevantproducts, such as catalysts, surfactants, acids, such as hydrofluoricacid, sulfates, drying agents, reaction auxiliaries, and the like. Notleast on account of the numerous possible uses of sulfuric acid, it isclear that there is a high demand for it: accordingly, worldwideproduction of sulfuric acid has exceeded the order of magnitude of 200million metric tonnes per annum, making sulfuric acid globally the mostproduced chemical.

Against this background as well it is clear that in the production ofsulfuric acid using pyrite as starting material, large quantities ofpyrite cinder or roasted pyrites result. These, generally speaking, arethe waste or residue arising in the form of pyrite from the roasting ofthe starting materials and starting ores employed. Roasted pyrites, inparticular, comprise a solid residue arising in the production of sulfurdioxide or sulfuric acid by thermal treatment of pyrite. The generalassumption is that on a worldwide basis, at least 20 million metrictonnes of roasted pyrites are obtained annually in connection with theproduction of sulfuric acid.

The roasted pyrites are generally stored or land filled at the site ofproduction, there already being very large stocks of roasted pyritespresent on a worldwide basis in connection with the production ofsulfuric acid, which has been practiced from the end of the 19th Centuryonward. Since the pyrite forming the basis for the production ofsulfuric acid, before being processed, is generally comminuted orground, the resulting roasted pyrites take the form, generally, of afinely particulate and, in particular, relatively homogeneous substance.

As far as the resulting pyrite cinder or roasted pyrites, generally, areconcerned, they comprise large amounts of iron and also economicallyrelevant amounts of further metals, including noble metals as well,which are not removed from the starting material in the course ofsulfuric acid production, meaning that roasted pyrites as such, againstthis background, are a valuable raw material for the recovery ofeconomically relevant quantities of metals, including noble metals.

In particular, roasted pyrites comprise iron oxides in the form of FeO,Fe₂O₃ (hematite) and/or Fe₃O₄ (magnetite), and residual amounts of FeS₂(iron disulfide), which are responsible in particular for the reddishcoloration of roasted pyrites. As well as silicon dioxide (SiO₂) andsulfates, particularly in the form of calcium sulfate (CaSO₄), roastedpyrites also include significant quantities of the metals zinc, copper,cobalt, titanium, manganese, vanadium, chromium and lead. Furthermore,roasted pyrites also comprise noble metals, more particularly in theform of gold and/or silver. In this regard as well, roasted pyritesharbor a not least economically high potential in relation to theextraction or recovery of metals, non-noble nonferrous metals, and noblemetals.

In this respect it is also notable that iron, with a weight fraction of95% in relation to the total metals utilized, is the most widely usedmetal globally. Iron, for example, constitutes the principal constituentof steel. The reason for the extensive use of iron lies not only in itswide availability but also, in particular, in the fact that iron hasoutstanding properties in respect of strength and toughness, especiallyinsofar as iron is present in the form of alloys with other metals, suchas chromium, molybdenum, and nickel. On account of these properties,iron is a basic material for many sectors of industry. In particular,iron in the form of steel is used in producing vehicles, ships, andacross the construction sector, as steel-reinforced concrete, forexample. A further factor is that iron represents a ferromagnetic metaland, consequently, is also important for large-scale industrial use inthe area of electromagnetism, such as in generators, transformers,electrical inductors, relays, and electrical motors. In this context,iron is used either in pure form or in combination, for example, withsilicon, aluminum, cobalt or nickel as a soft-magnetic core material forthe guiding of magnetic fields and/or for the shielding of magneticfields, or for increasing the inductivity. Iron is also used in thechemical sector, especially in the form of iron powder. In 2010,worldwide production of crude iron exceeded the figure of 1000 millionmetric tonnes. This shows that on a worldwide basis there is a very highdemand for iron.

Against this background, initial approaches in the prior art have beenpursued into making economic use of the roasted pyrites resulting as awaste product of sulfuric acid production.

Thus, for example, the residue in the form of pyrite cinder or roastedpyrites that remains in the getting of sulfuric acid is used in blastfurnaces. The focus in this regard is on the obtention of iron, with theunderlying methods occasionally not being economically andenvironmentally optimal, however, and recovery of further substances notbeing provided.

Furthermore, U.S. Pat. No. 4,259,106 A relates to a method for theroasting of an iron-containing starting material, such as roastedpyrites, which also comprises further metals, the intention being tosubject the further metals to a chlorination. With regard to thechlorinating reagent, calcium chloride is the authoritative referencepoint. In this context, chlorination only of non-iron metals isenvisaged, the intention being that iron as such should remain in themelt. A disadvantage, moreover, is the high energy consumptionassociated with the underlying method.

Moreover, GB 1 236 345 A is not aimed at recovery of iron specifically.In particular, the intention is only that there should be chlorinationof non-iron metals at the same time as the roasting of the startingmaterial. On the basis of the chlorinating agents used and the processregime selected, moreover, there is a high resulting corrosion activity,which is detrimental particularly to the apparatus on which the methodis based.

Furthermore, EP 0 538 168 A1 is not directed to the chlorination andrecovery of iron from roasted pyrites. Instead, this document is aimedat optimizing the cyanide leaching indicated for the recovery of goldand silver, there being no intention to recover metallic iron. Theprocess regime selected, moreover, is economically disadvantageous.

Furthermore, CN 101 067 163 A describes a treatment method for pyritewhere neither roasting nor chlorination is envisaged. For this reason aswell, the isolation of individual components from the raw material isnot very efficient.

Furthermore, CN 102 605 172 A relates to a method involving pyriteroasting, which envisages subsequent reduction of the cinder using abiomass. As a result of the carbon present in the biomass, the aim is toreduce iron(III) oxide to metallic iron. The resulting metallic iron isto be isolated via magnetic separation. Extensive recovery of furthermetals is not envisaged.

Moreover, CN 102 502 527 A is geared to the use of iron sulfate as astarting substance, which with pyrite and elemental sulfur is to bereacted to give iron powder. Chlorination within the recovery process isnot envisaged. Selective separation of different metal components is noteffectively ensured.

CN 102 251 067 A is aimed at a treatment of pyrite or pyrite cinderwithout chlorination, the intention being to remove metallicconstituents by means of leaching methods. Disadvantages here, however,are the high level of chemical usage and also the occasionally lowselectivity of the separation procedure.

CN 102 225 374 A relates to magnetic separation of iron followingremoval of other metals from pyrite cinder. Chlorination of metalliccomponents is not envisaged. Nor is targeted and selected separation ofdifferent metal components envisaged.

Furthermore, CN 102 121 059 A relates to a roasting method for pyrite.Chlorination of metallic components is not described. Furthermore, ironis reduced using carbon. A disadvantage in this case, however, is thatoccasionally the resulting metallic iron is not of high purity, sinceimpurities may result from the carbon used for the reduction.

CN 102 344 124 A describes the conversion of iron sulfate via themonohydrate form into sulfuric acid, iron and iron oxide, with pyritebeing used as starting material. There is no description of specificchlorination. Similarly, extensive separation and recovery of differentmetals is not envisaged.

Moreover, GB 1 350 392 A relates to the obtention of non-noblenonferrous metals from pyrite after roasting and chlorination of thenon-noble nonferrous metals. Chlorination of iron is not envisaged. Theiron component is to remain in the form of iron oxide in the residue.Accordingly, efficient separation of all the components is not possible.

U.S. Pat. No. 4,576,812 A relates to a method whereby iron chloride isused as a chloride source: starting from iron chloride and employingoxygen, the aim subsequently is to produce iron (III) oxide, which isthen used for the recovery of iron. Roasting of the starting material isnot described, and so occasionally dispersant starting materials arepresent.

Furthermore, DE 2 005 951 A is directed to a method for processingpyrite cinder to form feedstocks for blast furnaces. The pyrite cinderin this case is to be pelletized and burnt in a rotary furnace in thepresence of calcium chloride, the purpose of the calcium chloride beingto oxidize the iron. No further processing or separation is envisaged,and/or is impossible on account of the specific process regime.

DE 637 443 A relates to the reduction of iron chloride using steam andoptionally coal, starting from materials containing ferrous sulfide, theaim being to obtain elemental sulfur.

The scientific publication Trumbull R. C. et al., “Transactions of theInstitution of Mining and Metallurgy”, 58, 1949, pages 1 to 31, relatesto a method for the treatment of pyrite cinder according to theso-called Henderson process. In accordance with this method, the pyritecinder is first of all comminuted and then subjected to roasting in thepresence of sodium chloride. From the residue obtained in this way,non-noble nonferrous metals are removed. There is, however, no intentionof recovering iron from the pyrite cinder treated in this way. Theroasting takes place in the presence of sodium chloride at temperaturesof above 350° C. and in the presence of oxygen.

The scientific publication Pitsch H. et al., Revista de Metalurgia, 6,1970, pages 490 to 500, relates to a method for removing non-noblenonferrous metals from pyrite cinder using chlorinating reagents in theform of chlorine gas or calcium chloride. There is no intention torecover iron from the treated pyrite cinder. The pyrite cinder ischlorinated in an oxidizing atmosphere at high temperatures at 1000 to1200° C., with the consequence that any resultant iron(III) chloride isimmediately converted to iron (III) oxide and, consequently, there is noiron(III) chloride present after the chlorination.

The processing methods known in the prior art for metallic ores,especially pyrite, or for waste products arising in the processing ofthese ores, such as roasted pyrites, are therefore often associated withthe drawback that on the one hand the underlying methods are technicallycomplex and are carried out using a high volume of chemicals, andsecondly that comprehensive separation and/or recovery of differentmetal components is not possible. Equally, some of the plant used forthe methods in question, owing to the complex process regime, is costlyand inconvenient.

BRIEF SUMMARY OF THE INVENTION

Against this technical background, therefore, the object addressed bythe present invention is that of providing an efficient method and acorresponding plant and device for obtaining or recovering raw materialfrom ores and/or ore residues, and/or for recovering in particular ironor iron compounds, more particularly in the form of iron chloride, andalso, optionally, further components, in particular from roasted pyritesarising in the production of sulfuric acid, where the disadvantagesoutlined above, affecting the prior art, are to be at least largelyavoided or else at least attenuated.

An object of the present invention is seen in particular as being thatof providing an efficient method and relevant plant and/or devices, theaim thereof being to permit extremely comprehensive and selectiverecovery in particular of iron or iron compounds, more particularly ironchloride, from the parent roasted pyrites or residue. In this case, theintention is for the method and the corresponding plants to also permitin addition to this the removal or recovery of a large number ofdifferent metals, and also noble metals, from the parent roasted pyrite,selectively and with high purity.

Furthermore, a further object of the present invention lies in theprovision of a highly efficient method, minimizing the usage ofchemicals or of energy, for the recovery of iron, or iron compounds,more particularly iron chloride, from a parent pyrite residue or roastedpyrites, particularly with regard to recycling or re-utilization of theprocess chemicals used as part of the recovery procedure.

Moreover, according to a further objective of the present invention, theaim is to provide corresponding plant or devices which allow anefficient regime for the selective recovery in particular of iron andiron compounds, such as iron chloride, from the pyrite residue orroasted pyrites, where the plants and devices in question are at thesame time also to be optimized from an economic and environmentalstandpoint.

The objective outlined above is achieved in accordance with theinvention by the subject matter claimed herein, which concerns themethod of the invention for obtaining/recovering metallic iron or ironcompounds, more particularly iron chloride, from ores or ore residues,preferably from pyrite residues, more preferably from roasted pyritesobtained in the production of sulfuric acid; further advantageousembodiments and developments of this aspect of the invention are subjectmatter of the corresponding co-independent method claim and also of theunderlying dependent method claims.

Further provided by the present invention is additionally the recoveryplant of the invention, preferably for obtaining/recovering metalliciron and/or icon compounds, more particularly iron chloride, from oresor ore residues, preferably from pyrite residues, very preferably fromroasted pyrites obtained in the production of sulfuric acid, as definedin the corresponding independent claim relating to the plant of theinvention; further advantageous embodiments and developments of theplant of the invention are subject matter of the correspondingco-independent claim and the dependent claims relating to the plant ofthe invention.

Moreover, the present invention provides for the use of the recoveryplant according to the invention in the method of the invention forobtaining/recovering iron or iron compounds, more particularly ironchloride, from ores and/or ore residues in accordance with the relevantuse claim.

It will be appreciated that configurations, embodiments, advantages andthe like which are cited below in relation only to one aspect of theinvention, in order to avoid repetition, are of course equally valid inrelation to the other aspects of the invention.

It will further be appreciated that in the context of values, numbersand ranges specified below, the specified ranges should not beinterpreted as imposing any restriction; it is self-evident that, byvirtue of the specific case or specific application, deviations may bemade from the stated ranges and figures, without departing the scope ofthe present invention.

It is the case, moreover, that all value and parameter indications givenhereinafter, or the like, can fundamentally be ascertained or determinedusing standardized or explicitly stated determination methods or elsewith determination methods that are familiar per se to the skilledperson.

For all of the relative or percentage, especially weight-based, quantityfigures stated hereinafter, moreover, it should be borne in mind that inthe context of the present invention, these figures should be selectedand/or combined in such a way that the total—possibly including furthercomponents or ingredients or constituents, especially as definedhereinafter—always results as 100% or 100 wt %. This, however, isself-evident to the skilled person.

On this basis, the present invention is described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation or overview of the method of theinvention for obtaining raw material from ores or ore residues, moreparticularly for recovering metals from ores or ore residues, preferablyfor recovering metals from pyrite residues, more preferably from roastedpyrites obtained in the production of sulfuric acid;

FIG. 2 shows a further schematic representation or overview of themethod of the invention, according to a further inventively preferredembodiment.

FIG. 3 shows a schematic representation or overview of the recoveryplant A of the invention, preferably for obtaining raw material fromores or ore residues, more particularly for recovering metals from oresor ore residues, preferably for recovering metals from pyrite residues,more preferably from roasted pyrites obtained in sulfuric acidproduction;

FIG. 4 shows a further schematic representation or overview of therecovery plant A of the invention, in accordance with a furtherinventive embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A subject of the present invention, therefore—according to a firstaspect of the present invention—is a method for obtaining/recoveringmetallic iron and/or iron compounds, more particularly iron chloride,from ores and/or ore residues, more particularly a method for recoveringmetals from ores and/or ore residuals, preferably from pyrite residues,more preferably from roasted pyrites obtained in the production ofsulfuric acid, where the method comprises the following method steps:

-   -   (a) providing, more particularly processing, of a starting        material in the form of at least one ore and/or ore residue,        more particularly of at least one pyrite residue, preferably of        one or more roasted pyrites obtained in the production of        sulfuric acid, where the starting material comprises        -   i) iron, preferably as main constituent, and        -   ii) at least one noble metal, more particularly gold and/or            silver, and also        -   iii) at least one further metal, preferably selected from            the group of copper, zinc, lead, cobalt, titanium,            manganese, vanadium and chromium, more preferably selected            from the group of copper, zinc, lead and cobalt;    -   (b) oxidation treatment, more particularly calcining and/or        oxidative roasting, of the starting material provided in method        step (a), preferably using at least one oxidizing agent, more        particularly oxygen, to give iron oxide and oxides of the        further metals;    -   (c) chlorination of the oxidation products, more particularly of        iron oxide and oxides of the further metals, using at least one        chlorinating agent, more particularly a recyclable chlorinating        agent, comprising the chlorination of iron oxide and oxides of        the further metals to give iron chloride, more particularly        iron(III) chloride, and chlorides of the further metals;    -   (d) selective removing and/or isolation of iron chloride, more        particularly iron(III) chloride, from the product mixture        obtained in method step (c), and optional subsequent removing of        chlorides of the further metals from the product mixture freed        from iron chloride, the selective removing and/or isolation of        iron chloride, more particularly iron (III) chloride, taking        place by sublimation of the iron chloride, more particularly        iron(III) chloride, and the iron chloride, more particularly        iron(III) chloride, removed selectively in this way is obtained        as such by subsequent desublimation, or the iron chloride, more        particularly iron (III) chloride, removed selectively in this        way is subjected to reduction to give metallic iron;        where the above-stated method steps (a) to (d) are carried out        in the order listed above.

The method of the invention therefore relates significantly to thetargeted or selective obtaining of raw material of metallic iron and ofiron compounds more particularly from pyrite residues and, preferably,from roasted pyrites obtained in the production of sulfuric acid. Themethod of the invention thus relates to the targeted or selectiverecovery, more particularly from pyrite residues and, preferably, fromroasted pyrites obtained in the production of sulfuric acid. Aparticular focus of the method according to the invention lies in thiscase on the targeted isolation of iron, which, in accordance with theinvention, both, in particular, in the form of iron chloride as animportant commercial and industrial product, and in the form of metalliciron as a significant raw material, especially for the metal industry,can be provided. In this case, both metallic iron as such and thecorresponding iron compounds (specifically in the form of iron chloride,preferably in the form of iron (III) chloride) can be provided with highpurity.

As a result of the selective sublimation of iron chloride, moreparticularly iron (III) chloride (FeCl₃), from the product mixture it ispossible to realize a controlled removing of the iron component from theproduct mixture, so that on this basis, so to speak, the main componentof the starting material used, namely iron, can be isolated or removed,specifically in the form of the corresponding iron chloride. Thisselective sublimation or removing of iron chloride takes place inparticular on the basis of the deliberate selection of the sublimationtemperature. The reason is—without wishing to be confined to thistheory—that the iron chloride, more preferably iron(III) chloride(FeCl₃), that is to be removed and/or isolated has sublimationproperties differing from those of the chlorides of the further metalsand/or further components in the product mixture, especially in terms ofthe fact that iron chloride, particularly in comparison to the otherchlorides, has a lower sublimation temperature. Through the specificselection of the sublimation temperature it is possible, therefore, tocarry out selective removal of the iron component from the productmixture.

In accordance with the invention, the iron chloride obtained or isolatedmay on the one hand be provided and, on the other hand, furtherprocessing to metallic iron may be envisaged, by means of reduction. Inparticular for this purpose it is possible for corresponding sub-streamsof the sublimed iron chloride to be used in each case for thedesublimation and for the reduction, respectively. Accordingly, inmethod step (d), a particular possible procedure is for the ironchloride, more particularly iron (III) chloride, removed selectivelybeforehand by sublimation to be obtained as such at least partly bymeans of subsequent desublimation and for the iron chloride, moreparticularly iron (III) chloride, removed selectively in this way to besubjected at least partly to a reduction to give metallic iron, moreparticularly with prior division of the sublimed iron chloride into twosub-streams.

With regard to the iron chloride, more particularly iron(III) chloride(FeCl₃), removed from the product mixture and, in particular, sublimed,this chloride may thus be recovered as such: for this purpose, theremoved and/or isolated and in particular sublimed iron chloride, moreparticularly iron (III) chloride (FeCl₃), may be desublimed to give, inparticular, solid and/or purified iron chloride, more particularlyiron(III) chloride (FeCl₃). The desublimation may be carried out in acorresponding desublimation or condensation device. In this context, inparticular, gaseous iron chloride may be transferred from thesublimation device into the desublimation device. In this way, inparticular, particulate or solid iron chloride is obtained, which assuch constitutes an economically relevant industrial or commercialproduct, particularly with regard to its use as a pigment and/orflocculate and/or precipitant, especially in wastewater treatment plantsor the like.

Furthermore, the removed and/or isolated and more particularly sublimedand therefore gaseous iron chloride, more particularly iron (III)chloride (FeCl₃), may be reduced to give metallic iron. In this contextit is possible to use at least one reducing agent. The reducing agent ispreferably hydrogen or natural gas (especially methane), more preferablyhydrogen.

Furthermore, the removing of the iron component, which generallyrepresents a main constituent or a main component of the pyrite cinderor roast pyrites employed in accordance with the invention, takes placein particular, in the sequence of the method to logical procedure,before the optionally provided removing or recovery of the othercomponents. Accordingly, the main component is removed at a very earlystage, which firstly leads to high yields in respect of iron as such butalso with regard to the removing of further components. This is because,on the basis of the method routine of the invention, as a result of theremoving of iron, the relative proportions of the other components inthe product mixture freed of iron are increased accordingly, therebyproviding optimization, in turn, of recovery of these raw materials,downstream of or subsequent to the recovery of iron, especially withregard to reduced deployment of chemicals and/or energy for the purposeof removing the further, non-iron metal components and/or the noblemetals. This approach in accordance with the invention thus raises theoverall efficiency of the recovery of the further metal componentsand/or noble metals.

The roasted pyrites used according to the invention are in particularroasted pyrites which originate from the production of sulfuric acid.Roasted pyrites are obtained, in particular, as waste or residue as partof sulfuric acid production. This method of the invention is associatedwith the central advantage that a large number of raw materials, on thebasis of metals and/or metal compounds, can be obtained or isolated fromthe underlying starting material—which is present as waste material inlarge quantities; in this context, the method of the invention equallypermits a high selectivity in relation to the metal components to beobtained from the starting material. In particular, the method of theinvention also permits effective recovery or purification of noblemetals, such as gold or silver, that are present in the startingmaterial. Overall, the invention thus provides extensive utilization ofthe starting material with high selectivity of the material removal.

By virtue of the specific procedure according to the present invention,moreover, at least substantially complete digestion of the startingmaterial is possible, with the possibility being provided equally of theprovision of high-purity end products from the starting material,thereby ensuring overall, in relation to the purified metal components,high qualities and purities as well.

A further central idea in the present invention can be seen, moreover,in the fact that the chlorinating agent used for the chlorination of themetal components, which according to one inventively particularlypreferred embodiment, as outlined below, is ammonium chloride (NH₄Cl),can be recycled or regenerated. It should also be emphasized in thiscontext that the starting materials or components used for the recyclingare equally obtained themselves or are provided as part of the method ofthe invention or processing sequence, and so in this way there is afurther optimization, particularly since there is no need for theadditional use of chemicals for the recycling.

With regard to “recycling” as it is used in the context of the presentinvention in relation to the chlorinating agent, this term should beunderstood very broadly. In particular, the term “recycling” pertains torenewed obtention of chlorinating agent used beforehand for thechlorination of the metal components as part of the method of theinvention, and exhausted or degraded. The recycling in this case takesplace in particular on the basis of chemical reactions, whereby inparticular, degradation products originating from the chlorinating agentin the chlorinating process are isolated and used as starting materialin subsequent chemical reactions with a corresponding co-reactant forthe renewed obtention of the chlorinating agent as a recyclate. As setout in detail below, the chlorinating agent used in accordance with theinvention is, in particular, ammonium chloride (NH₄Cl), and thedegradation product obtained as part of the chlorination procedure,namely ammonia (NH₃), is reacted preferentially with an inorganicchlorine compound, more particularly hydrogen chloride, therebyproducing the recyclate, namely ammonium chloride, which can in turn beused again as a chlorinating agent.

A further advantage of the method of the invention is to be seen in thefact that, as mentioned above, the starting substances needed for therecycling, particularly as part of the method of the invention, arethemselves generated or obtained, meaning that in relation to thechlorinating agent it is possible, so to speak, for a closed circuit toresult, especially as regards the chlorine constituent, hand in handwith an increased efficiency of the method of the invention, withsimultaneously reduced costs and improved environmental balance. In thecontext of the present invention, however, it is equally possible forthe starting materials for the recycling of the chlorinating agent,especially with regard to the inorganic chlorine compound, to be addedexternally. Against this background as well, the method of the inventionfeatures high flexibility, and so the method of the invention, so tospeak, can be individually adapted or tailored to some extent againstthe background of the specific process carried out, as defined below,including in relation to the recycling of the chlorinating agent.

The procedure according to the invention results in a method which isoptimized just as much economically as it is environmentally, withreduced production of waste materials and waste gases, the requireddeployment of energy for the implementation of the method being reducedat the same time.

In summary, therefore, the present invention for the first time providesa method for the targeted or selective processing particularly of pyriteresidues, such as roasted pyrites, that allows an efficient andcomprehensive utilization of the waste material or residue—inparticular, roasted pyrites originating from sulfuric acid production.It is also important in this regard that the pyrite residues or roastedpyrites in question are available in large quantities for use as aresult of the decades-long production of sulfuric acid, meaning that inaccordance with the invention it is possible to have recourse toresources that are of corresponding extensiveness. In this context, afurther advantage of the approach according to the invention is thatfrom environmentally specific aspects as well, occasionally notunproblematic stockpiles of the aforesaid pyrite residues or roastedpyrites can be consumed or reduced.

As mentioned above, the starting material used in the method of theinvention contains a multiplicity of metals and metal components, withiron generally constituting a main constituent. With regard to theparent iron and also the other metallic components, such as copper,zinc, lead, cobalt, titanium, manganese, vanadium and chromium, they arepresent in particular not in metallic form as such, in the startingmaterial used for the method of the invention, but instead in the formof corresponding metal-containing compounds, more particularly in theform of oxides, and in this respect as well the respective metals may bepresent in different oxidation states. Accordingly, for iron, inrelation to the starting material, the case is typically that iron maybe present, for example, as iron (II) oxide, iron (II, III) oxide and/oriron (III) oxide, particularly as indicated further below. Furthermore,for the noble metals present in the starting material, preferably inrelation to gold, it is the case that the respective noble metals,preferably gold, are present in metallic form in the starting material.With regard to the silver present in the starting material, it maygenerally be present in the starting material in the form of a compound,more particularly as oxide, but also in metallic form.

In the context of the present invention it has proven particularlyadvantageous if in method step (c) the chlorination is carried out usingammonium chloride as chlorinating agent. In particular, therefore,ammonium chloride (NH₄Cl) ought to be used as chlorinating agent inmethod step (c). In this context, provision may be made in particularfor the ammonium chloride (NH₄Cl) to be used as especially particulatesolid and/or as pure substance. The inventively preferably envisaged useof a specific chlorinating agent in the form of ammonium chloride isassociated in particular with the advantage that ammonium chloride isoutstandingly suitable for recycling and, furthermore, has goodapplications properties, not least in respect of its relatively lowtoxicity and its presence as a solid, which improves meterability.

In accordance with the invention, the chlorinating agent, moreparticularly ammonium chloride, may be supplied to the chlorinatingdevice or introduced into the chlorinating device for the purposes ofthe chlorination of the oxidation products and/or of aforementionedmetals.

In particular in relation to the use of a specific chlorinating agent inthe form of ammonium chloride, the conditions within the method of theinvention may be such that in method step (c), in the chlorination,especially gaseous ammonia (NH₃) and, optionally, especially gaseouswater, preferably especially gaseous ammonia (NH₃), results or result.In this context, in particular, gaseous ammonia (NH₃) may result as areaction product originating from the chlorination from the chlorinatingagent, more particularly ammonium chloride (NH₄Cl). In this regard,reference may be made in particular to the reaction equation (iii)below.

In accordance with the invention, provision may be made in particularfor the chlorinating agent used in method step (c), more particularlyammonium chloride (NH₄Cl), to be recycled by recovery and/or removal ofreaction products resulting from the chlorinating agent in thechlorination of the aforementioned metals and/or oxidation products,more particularly of preferably gaseous ammonia (NH₃), and by subsequentreaction of the reaction products, more particularly of preferablygaseous ammonia (NH₃), with a preferably inorganic chlorine compound,more particularly hydrogen chloride (HCl).

In particular, the recycling of the chlorinating agent, moreparticularly ammonium chloride (NH₄Cl), may be carried out in a reactionor condensation device.

In this context, in accordance with the invention, the procedure, forexample, may be such that ammonia (NH₃) resulting in the chlorination ofthe metals and/or oxidation products is taken off from the chlorinatingdevice and introduced into a reaction or condensation device, where itis reacted with the inorganic chlorine compound likewise introduced intothe reaction or condensation device, more particularly hydrogen chloride(HCl), in order to give ammonium chloride (NH₄Cl). In this way, thechlorinating agent, more particularly in the form of ammonium chloride(NH₄Cl), can be recycled and supplied again to the chlorinatingoperation. On the basis of this inventive procedure, therefore, afurther method optimization is ensured in the context of the presentinvention.

With regard to the reaction or conversion of ammonia (NH₃), on the onehand, and of the inorganic chlorine compound, more particularly hydrogenchloride (HCl), on the other, this reaction or conversion underlyingrecycling of the chlorinating agent, the reaction or conversion may takeplace in particular in the gas phase, in particular with resultingammonium chloride (NH₄) resulting or condensing in solid phase. On thebasis of this specific inventive procedure therefore, especiallyparticulate ammonium chloride is obtained as a solid in high purity,this being associated with corresponding advantages in the context ofthe subsequent chlorination.

In particular, therefore, provision may be made in the present inventionfor the reaction products resulting from the chlorinating agent, moreparticularly ammonia (NH₃) on the one hand and the preferably inorganicchlorine compound, more particularly hydrogen chloride (HCl) on theother, to be reacted in the gas phase, in particular to give ammoniumchloride (NH₄Cl), preferably as an especially particulate solid and/oras pure substance.

The underlying reaction for the recycling of ammonium chloride may takeplace in particular according to the following reaction equation (i):NH₃+HCl→NH₄Cl.  (i)

In accordance with the invention, provision may further be made for theresulting or recycled chlorinating agent, more particularly ammoniumchloride (NH₄Cl), to be used again in method step (c), more particularlyby renewed supply or renewed introduction into the chlorinating device.In particular the resulting or recycled chlorinating agent, moreparticularly ammonium chloride (NH₄Cl), may be supplied again to theoxidation products for chlorination and/or to the product mixtureresulting from method step (b), in method step (c).

The preferably inorganic chlorine compound, more particularly hydrogenchloride (HCl), can be obtained, according to one particular embodimentof the present invention, by the reduction of iron chloride carried outoptionally in method step (d), more particularly with use of a reducingagent, preferably hydrogen or natural gas (more particularly methane),preferably hydrogen. For example, the preferably inorganic chlorinecompound, more particularly hydrogen chloride (HCl), may be obtained byreduction of iron chloride.

In this context, in accordance with the invention provision may be madein particular, in relation to the recycling of the chlorinating agent,for the preferably inorganic chlorine compound, more particularlyhydrogen chloride (HCl), to be obtained by the optionally providedreduction of iron chloride, preferably iron(III) chloride (FeCl₃),obtained in method step c), more particularly with use of a reducingagent, preferably hydrogen or natural gas (especially methane), morepreferably hydrogen.

Equally, the inorganic chlorine compound, more particularly hydrogenchloride (HCl), that is used for the recycling may also be obtained fromthe optional reduction of the chlorides of the further metals obtainedin method step (c), more particularly as defined above.

In view of the concept according to the invention, with the specificrecycling of the chlorinating agent, the respective substances orreactants can be provided within the method of the invention itself,meaning that there is so to speak a closed circuit in terms of thechlorinating agent, this going hand in hand with a reduced level ofchemicals used and hence also, in particular, with an improvedenvironmental and economic balance on the part of the method of theinvention.

In method step (d) the reduction of the removed and more particularlysublimed iron chloride, more particularly iron (III) chloride, should becarried out using at least one reducing agent. The reducing agent usedis very preferably hydrogen. Especially where hydrogen is used asreducing agent, the reduction described above may result not only inmetallic iron but also in hydrogen chloride (HCl).

In this context there may equally be provision for, as indicated above,the hydrogen chloride (HCl) resulting in the reduction to be used forthe recycling of the chlorinating agent, preferably ammonium chloride(NH₄Cl), especially as defined above. In this context there may equallybe provision for the especially gaseous ammonia (NH₃), on the one hand,and the hydrogen chloride (HCl), on the other, resulting in thechlorination in method step (c), to be combined and/or brought intocontact and reacted to give the recycled chlorinating agent, preferablyammonium chloride (NH₄Cl). In particular it is possible in this context,as described above, to carry out the procedure in a reaction orcondensation device. In this context there may in particular beprovision, in accordance with the invention, for the gaseous ammonia(NH₃) from the chlorinating device, on the one hand, and the hydrogenchloride (HCl) on the other hand, to be taken off in each case from thereduction device and introduced in each case into the reaction orcondensation device, and reacted to give ammonium chloride (NH₄Cl).

The metallic iron obtained in accordance with the invention is notablefor a high purity. Hence in accordance with the invention it may be thecase that the metallic iron obtained has a purity of at least 90 wt %,more particularly at least 95 wt %, preferably at least 98 wt %, morepreferably at least 99 wt %, very preferably at least 99.5 wt %,especially preferably at least 99.99 wt %, calculated as element andbased on the metallic iron obtained.

The high purity of the resulting metallic iron is accompanied bycorresponding positive properties of the iron, especially in respect ofa high magnetic saturation, high electrical conductivity and good acidresistance. The high-purity metallic iron obtained on the basis of themethod of the invention, as a commercial product, also corresponds inparticular to the quality requirements or quality features of so-calledcarbonyl iron or ARMCO iron.

Not least on the basis of the high proportion of iron in the startingmaterial indicated above, it is possible in accordance with theinvention to realize overall high yields in conjunction with highproduct quality of the metallic iron obtained.

In view of the inventive method regime with the controlled oxidation,chlorination and selective sublimation, the iron component can beisolated effectively from the parent starting material, resulting inhigh product yields. In this context, the product mixture obtained inmethod step (d) and freed from iron chloride, preferably iron (III)chloride (FeCl₃), can have a (residual) iron content of less than 10 wt%, more particularly less than 5 wt %, preferably less than 3 wt %,calculated as element and based on the dry weight of the productmixture. Correspondingly, therefore, in relation to the product mixtureobtained in method step (d) and freed from iron, there is a rise in therelative proportion of the other components, and so these componentsare, so to speak, concentrated in relation to the resulting productmixture, thereby also further improving their subsequent removing orpurification and also leading in this respect to higher yields.

In accordance with this aspect of the present invention, the presentinvention thus relates equally to a method for obtaining/recoveringmetallic iron and/or iron compounds, more particularly iron chloride,from ores and/or ore residues, preferably from pyrite residues, morepreferably from roasted pyrites obtained in the production of sulfuricacid, more particularly as defined in one of the preceding claims, wherethe method comprises the following method steps:

-   -   (a) providing, more particularly processing, of a starting        material in the form of at least one ore and/or ore residue,        more particularly of at least one pyrite residue, preferably of        one or more roasted pyrites obtained in the production of        sulfuric acid, where the starting material comprises        -   i) iron, preferably as main constituent, and        -   ii) at least one noble metal, more particularly gold and/or            silver, and also        -   iii) at least one further metal, preferably selected from            the group of copper, zinc, lead, cobalt, titanium,            manganese, vanadium and chromium, more preferably selected            from the group of copper, zinc, lead and cobalt    -   (b) oxidation treatment, more particularly calcining and/or        oxidative roasting, of the starting material provided in method        step (a), preferably using at least one oxidizing agent, more        particularly oxygen, to give iron oxide and oxides of the        further metals;    -   (c) chlorination of the oxidation products, more particularly of        iron oxide and oxides of the further metals, obtained in method        step (b), using at least one chlorinating agent, more        particularly a recyclable chlorinating agent, comprising the        chlorination of iron oxide and oxides of the further metals, to        give iron chloride, more particularly iron(III) chloride, and        chlorides of the further metals,        -   where the chlorination is carried out using ammonium            chloride as chlorinating agent,        -   where the chlorinating agent, more particularly ammonium            chloride (NH₄Cl), is recycled by recovery and/or removing of            reaction products resulting from the chlorinating agent in            the chlorination of the oxidation products, more            particularly of preferably gaseous ammonia (NH₃), and            subsequent reaction of the reaction products, more            particularly of preferably gaseous ammonia (NH₃), with a            preferably inorganic chlorine compound, more particularly            hydrogen chloride (HCl), in particular where the preferably            inorganic chlorine compound, more particularly hydrogen            chloride (HCl), is obtained by the reduction, carried out            optionally in method step (d), of iron chloride, especially            using a reducing agent, preferably hydrogen or natural gas            (especially methane), preferably hydrogen, and        -   where the chlorinating agent obtained and/or recycled, more            particularly ammonium chloride (NH₄Cl), is used again in            method step (c);    -   (d) selective removing of iron chloride from the product mixture        obtained in method step (c), and optional subsequent removing of        chlorides of the further metals from the product mixture freed        from iron chloride, where the selective removing of iron        chloride, more particularly iron(III) chloride, takes place by        sublimation of the iron chloride, more particularly iron (III)        chloride, and the iron chloride, more particularly iron (III)        chloride, removed selectively in this way is obtained as such by        subsequent desublimation or the iron chloride, more particularly        iron(III) chloride, removed selectively in this way is subjected        to reduction to give metallic iron;        where the above-stated method steps (a) to (d) are carried out        in the order listed above.

In general as far as the starting material is concerned that is used inthe method of the invention, particularly in the form of pyrite residuesor roasted pyrites, the starting material may comprise iron in the formof at least one iron oxide. In this context provision may be made inparticular for the starting material to comprise iron oxide in the formof iron (II) oxide (FeO), iron (III) oxide (Fe₂O₃) and/or iron (II, III)oxide (Fe₃O₄).

In this context the starting material may comprise iron, moreparticularly in the form of iron oxide, in amounts in the range from 10wt % to 75 wt %, more particularly in the range from 20 wt % to 70 wt %,preferably in the range from 30 wt % to 65 wt %, more preferably in therange from 40 wt % to 60 wt %, calculated as element and based on thedry weight of the starting material. As noted above, therefore, ironconstitutes the main component of the starting material to be processed,and so against this background as well, high recovery quantities oryields in respect of iron are made possible in the context of the methodof the invention.

Furthermore, the starting material may comprise the noble metal, moreparticularly gold and/or silver, in amounts in the range from 0.1 g/t to300 g/t, more particularly in the range from 0.5 g/t to 200 g/t,preferably in the range from 0.75 g/t to 100 g/t, more preferably in therange from 1 g/t to 50 g/t, calculated as element and based on the dryweight of the starting material. The above figures are based on the sumof the stated metals in the starting material.

The starting material may more particularly comprise gold in the form ofmetallic gold. Another reason in particular why gold is in metallic formis that on account of the noble physical properties of the element, itis not amenable to combustion in the presence of oxygen.

More particularly, in this context, the starting material may comprisegold in amounts in the range from 0.1 g/t to 15 g/t, more particularlyin the range from 0.2 g/t to 10 g/t, preferably in the range from 0.5g/t to 8 g/t, more preferably in the range from 1 g/t to 5 g/t,calculated as element and based on the dry weight of the startingmaterial.

The starting material may further comprise silver in the form ofmetallic silver and/or in the form of silver oxide, especially silver(I) oxide. As a noble metal, silver is generally relatively tardy inreactivity, but is less noble than gold, meaning that silver may asindicated above be present in the starting material at least partly inthe form of silver oxide, as well.

As far as the noble metal silver in the starting material is concerned,moreover, the starting material may comprise silver in amounts in therange from 1 g/t to 300 g/t, more particularly in the range from 2 g/tto 200 g/t, preferably in the range from 3 g/t to 100 g/t, morepreferably in the range from 5 g/t to 50 g/t, calculated as element andbased on the dry weight of the starting material.

In view of the presence of noble metals, more particularly gold and/orsilver, in relevant amounts, the starting material is also economicallysignificant in relation to the recovery of these noble metals. Inparticular, on the basis of the method of the invention, in addition tothe obtention of iron and other products of economic interest, anefficient and cost-effective method is also provided for the recovery ofnoble metals, such as gold and/or silver, from the parent startingmaterial, leading to a significant increase in the economics of themethod of the invention, since the noble metal components generally havea high material value.

Furthermore, the starting material may comprise the further metal, moreparticularly copper, zinc, lead, cobalt, titanium, manganese, vanadiumand/or chromium, preferably copper, zinc, lead and/or cobalt, in amountsin the range from 0.001 wt % to 10 wt %, more particularly in the rangefrom 0.005 wt % to 5 wt %, preferably in the range from 0.0075 wt % to 3wt %, more preferably in the range from 0.01 wt % to 2 wt %, calculatedas element and based on the dry weight of the starting material. Theabove figures are based on the sum of the stated metals in the startingmaterial.

With regard to the further metal in the form of copper in this context,the starting material may comprise copper in the form of copper oxide,more particularly copper (I) oxide and/or copper (II) oxide.

In this context the starting material may comprise copper, moreparticularly in the form of copper oxide, in amounts in the range from0.01 wt % to 5 wt %, more particularly in the range from 0.05 wt % to 3wt %, preferably in the range from 0.075 wt % to 2 wt %, more preferablyin the range from 0.1 wt % to 1 wt %, calculated as element and based onthe dry weight of the starting material.

With regard, moreover, to the further metal in the form of zinc, thestarting material may comprise zinc in the form of zinc oxide, moreparticularly zinc (II) oxide.

In this context, the starting material may comprise zinc, moreparticularly in the form of a zinc oxide, in amounts in the range from0.02 wt % to 10 wt %, more particularly in the range from 0.075 wt % to5 wt %, preferably in the range from 0.1 wt % to 3 wt %, more preferablyin the range from 0.2 wt % to 2 wt %, calculated as element and based onthe dry weight of the starting material.

With regard, moreover, to the further metal in the form of lead, thestarting material may comprise lead in the form of lead oxide, moreparticularly lead (II) oxide.

In this context, the starting material may comprise lead, moreparticularly in the form of a lead oxide, in amounts in the range from0.1 wt % to 5 wt %, more particularly in the range from 0.05 wt % to 4wt %, preferably in the range from 0.1 wt % to 2 wt %, more preferablyin the range from 0.15 wt % to 1.5 wt %, calculated as element and basedon the dry weight of the starting material.

With regard, moreover, to the further metal in the form of cobalt, thestarting material may comprise cobalt in the form of cobalt oxide, moreparticularly cobalt(II) oxide.

In this context, the starting material may comprise cobalt, moreparticularly in the form of a cobalt oxide, in amounts in the range from0.001 wt % to 2 wt %, more particularly in the range from 0.005 wt % to1 wt %, preferably in the range from 0.0075 wt % to 0.5 wt %, morepreferably in the range from 0.01 wt % to 0.1 wt %, calculated aselement and based on the dry weight of the starting material.

With regard, moreover, to the further metal in the form of titanium, thestarting material may comprise titanium in the form of titanium oxide.

In this context, the starting material may comprise titanium, moreparticularly in the form of a titanium oxide, in amounts in the rangefrom 0.001 wt % to 2 wt %, more particularly in the range from 0.005 wt% to 1 wt %, preferably in the range from 0.0075 wt % to 0.5 wt %, morepreferably in the range from 0.01 wt % to 0.1 wt %, calculated aselement and based on the dry weight of the starting material.

With regard, moreover, to the further metal in the form of manganese,the starting material may comprise manganese in the form of manganeseoxide.

In this context, the starting material may comprise manganese, moreparticularly in the form of a manganese oxide, in amounts in the rangefrom 0.001 wt % to 2 wt %, more particularly in the range from 0.005 wt% to 1 wt %, preferably in the range from 0.0075 wt % to 0.5 wt %, morepreferably in the range from 0.01 wt % to 0.1 wt %, calculated aselement and based on the dry weight of the starting material.

With regard, furthermore, to the further metal in the form of vanadium,the starting material may comprise vanadium in the form of vanadiumoxide.

In this context, the starting material may comprise vanadium, moreparticularly in the form of a vanadium oxide, in amounts in the rangefrom 0.001 wt % to 2 wt %, more particularly in the range from 0.005 wt% to 1 wt %, preferably in the range from 0.0075 wt % to 0.5 wt %, morepreferably in the range from 0.01 wt % to 0.1 wt %, calculated aselement and based on the dry weight of the starting material.

With regard, furthermore, to the further metal in the form of chromium,the starting material may comprise chromium in the form of chromiumoxide.

In this context, the starting material may comprise chromium, moreparticularly in the form of a chromium oxide, in amounts in the rangefrom 0.001 wt % to 2 wt %, more particularly in the range from 0.005 wt% to 1 wt %, preferably in the range from 0.0075 wt % to 0.5 wt %, morepreferably in the range from 0.01 wt % to 0.1 wt %, calculated aselement and based on the dry weight of the starting material.

Furthermore, the starting material may comprise at least one semimetal.In particular the semimetal may be selected from the group of silicon,arsenic, selenium, antimony, tellurium and combinations thereof, moreparticularly silicon. The starting material may comprise the semimetal,more particularly silicon, arsenic, selenium, antimony and/or tellurium,in amounts in the range from 1 wt % to 40 wt %, more particularly in therange from 2 wt % to 30 wt %, preferably in the range from 3 wt % to 20wt %, more preferably in the range from 4 wt % to 15 wt %, calculated aselements and based on the dry weight of the starting material. The abovefigures are based on the sum of the semimetals mentioned in the startingmaterial.

Furthermore, the starting material may comprise at least one transitionmetal, more particularly manganese and/or molybdenum.

In particular, the starting material may comprise silicon, moreparticularly in the form of silicon oxide, preferably silicon dioxide(SiO₂).

More particularly the starting material may comprise silicon, moreparticularly in the form of silicon oxide, in amounts in the range from0.5 wt % to 30 wt %, more particularly in the range from 1 wt % to 20 wt%, preferably in the range from 2 wt % to 15 wt %, more preferably inthe range from 3 wt % to 10 wt %, calculated as element and based on thedry weight of the starting material.

Furthermore, the starting material may comprise arsenic, moreparticularly in amounts of not more than 1 wt %, more particularly notmore than 0.5 wt %, preferably not more than 0.3 wt %, calculated aselement and based on the dry weight of the starting material.

The starting material may further comprise at least one alkali metaland/or alkaline earth metal, more particularly at least one alkalineearth metal, preferably calcium.

In particular, the alkali metal and/or alkaline earth metal, moreparticularly the alkaline earth metal, preferably calcium, may bepresent in the form of at least one salt, more particularly sulfate. Thestarting material may more particularly comprise calcium sulfate.

In this context, the starting material may comprise the alkali metaland/or alkaline earth metal, more particularly the alkaline earth metal,preferably calcium, more preferably in the form of calcium sulfate, inamounts in the range from 0.2 wt % to 20 wt %, more particularly in therange from 0.5 wt % to 15 wt %, preferably in the range from 1 wt % to10 wt %, more preferably in the range from 2 wt % to 8 wt %, calculatedas element and based on the dry weight of the starting material.

Furthermore, the starting material may comprise at least one nonmetal,more particularly selected from the group of carbon, nitrogen, sulfurand phosphorus, more particularly sulfur, preferably in the form of therespective salts.

In this context the starting material may comprise sulfur, moreparticularly in the form of sulfur-containing salts, preferablysulfides, such as iron disulfide, and/or, more preferably, sulfates.

In this context, the starting material may comprise sulfur in amounts inthe range from 0.2 wt % to 15 wt %, more particularly in the range from0.5 wt % to 10 wt %, preferably in the range from 1 wt % to 8 wt %, morepreferably in the range from 1.5 wt % to 6 wt %, calculated as elementand based on the dry weight of the starting material.

In accordance with the invention it may in particular be the case thatthe starting material, more particularly the pyrite residue or roastedpyrites, comprises the following ingredients, calculated in each case aselement and based in each case on the dry weight of the startingmaterial:

-   -   iron, more particularly in the form of iron oxide, for example        in amounts in the range from 10 wt % to 75 wt %, more        particularly in the range from 20 wt % to 70 wt %, preferably in        the range from 30 wt % to 65 wt %, more preferably in the range        from 40 wt % to 60 wt %;    -   gold, more particularly in amounts in the range from 0.1 g/t to        15 g/t, more particularly in the range from 0.2 g/t to 10 g/t,        preferably in the range from 0.5 g/t to 8 g/t, more preferably        in the range from 1 g/t to 5 g/t;    -   silver, more particularly in amounts in the range from 1 g/t to        300 g/t, more particularly in the range from 2 g/t to 200 g/t,        preferably in the range from 3 g/t to 100 g/t, more preferably        in the range from 5 g/t to 50 g/t;    -   copper, more particularly in the form of copper oxide, for        example in amounts in the range from 0.01 wt % to 5 wt %, more        particularly in the range from 0.05 wt % to 3 wt %, preferably        in the range from 0.075 wt % to 2 wt %, more preferably in the        range from 0.1 wt % to 1 wt %;    -   zinc, more particularly in the form of zinc oxide, for example        in amounts in the range from 0.02 wt % to 10 wt %, more        particularly in the range from 0.075 wt % to 5 wt %, preferably        in the range from 0.1 wt % to 3 wt %, more preferably in the        range from 0.2 wt % to 2 wt %;    -   lead, more particularly in the form of lead oxide, for example        in amounts in the range from 0.01 wt % to 5 wt %, more        particularly in the range from 0.05 wt % to 4 wt %, preferably        in the range from 0.1 wt % to 2 wt %, more preferably in the        range from 0.15 wt % to 1.5 wt %;    -   cobalt, more particularly in the form of cobalt oxide, for        example in amounts in the range from 0.001 wt % to 2 wt %, more        particularly in the range from 0.005 wt % to 1 wt %, preferably        in the range from 0.0075 wt % to 0.5 wt %, more preferably in        the range from 0.01 wt % to 0.1 wt %;    -   titanium, more particularly in the form of titanium oxide, for        example in amounts in the range from 0.001 wt % to 2 wt %, more        particularly in the range from 0.005 wt % to 1 wt %, preferably        in the range from 0.0075 wt % to 0.5 wt %, more preferably in        the range from 0.01 wt % to 0.1 wt %;    -   manganese, more particularly in the form of manganese oxide, for        example in amounts in the range from 0.001 wt % to 2 wt %, more        particularly in the range from 0.005 wt % to 1 wt %, preferably        in the range from 0.0075 wt % to 0.5 wt %, more preferably in        the range from 0.01 wt % to 0.1 wt %;    -   vanadium, more particularly in the form of vanadium oxide, for        example in amounts in the range from 0.001 wt % to 2 wt %, more        particularly in the range from 0.005 wt % to 1 wt %, preferably        in the range from 0.0075 wt % to 0.5 wt %, more preferably in        the range from 0.01 wt % to 0.1 wt %;    -   chromium, more particularly in the form of chromium oxide, for        example in amounts in the range from 0.001 wt % to 2 wt %, more        particularly in the range from 0.005 wt % to 1 wt %, preferably        in the range from 0.0075 wt % to 0.5 wt %, more preferably in        the range from 0.01 wt % to 0.1 wt %;    -   silicon, more particularly in the form of silicon dioxide, for        example in amounts in the range from 0.5 wt % to 30 wt %, more        particularly in the range from 1 wt % to 20 wt %, preferably in        the range from 2 wt % to 15 wt %, more preferably in the range        from 3 wt % to 10 wt %;    -   arsenic, for example in amounts of not more than 1 wt %, more        particularly not more than 0.5 wt %, preferably not more than        0.3 wt %;    -   calcium, more particularly in the form of calcium sulfate, for        example in amounts in the range from 0.2 wt % to 20 wt %, more        particularly in the range from 0.5 wt % to 15 wt %, preferably        in the range from 1 wt % to 10 wt %; and/or    -   sulfur, more particularly in the form of sulfur-containing salts        for example in amounts in the range from 0.2 wt % to 15 wt %,        more particularly in the range from 0.5 wt % to 10 wt %,        preferably in the range from 1 wt % to 8 wt %, more preferably        in the range from 1.5 wt % to 6 wt %.

The starting material here may comprise the following ingredients, basedin each case on the dry weight of the starting material:

-   -   iron (II, III) oxide (Fe₃O₄), more particularly in amounts in        the range from 10 wt % to 80 wt %, more particularly in the        range from 20 wt % to 70 wt %, preferably in the range from 30        wt % to 60 wt %;    -   iron (III) oxide (Fe₂O₃), more particularly in amounts in the        range from 5 wt % to 50 wt %, more particularly in the range        from 10 wt % to 40 wt %, preferably in the range from 15 wt % to        30 wt %;    -   silicon dioxide, more particularly in amounts in the range from        2 wt % to 30 wt %, more particularly in the range from 5 wt % to        25 wt %, preferably in the range from 10 wt % to 20 wt %; and/or    -   calcium sulfate, more particularly in amounts in the range from        1 wt % to 25 wt %, more particularly in the range from 2 wt % to        20 wt %, preferably in the range from 5 wt % to 15 wt %.

The underlying starting material, more particularly in the form ofpyrite residues or roasted pyrites, as obtained in particular in theproduction of sulfuric acid, therefore contains—alongside iron, moreparticularly in the form of iron oxides, as main constituent—numerousfurther metals or noble metals, meaning that the starting material usedin accordance with the invention is outstandingly suitable for use inthe context of the present invention, since a multiplicity of differentcomponents with industrial and economic relevance, based on metals ornoble metals, are recovered or obtained from the starting material, withthe method of the invention in this respect enabling selective andcomprehensive recovery of the components in question, including inparticular in the form of the respective metals.

With regard to the method of the invention as such, provision may bemade in accordance with the invention for comminution and/orhomogenization of the starting material to be carried out in method step(a), or before implementation of method step (b). In particular thestarting material may be adjusted to average particle sizes, moreparticularly average particle size D₅₀, in the range from 0.1 μm to 10cm, more particularly 1 urn to 5 cm, preferably 100 μm to 1 cm, morepreferably 500 μm to 0.5 cm. For this purpose it is possible to usecustomary comminuting apparatus well known per se to the skilled person,such as crushing and/or grinding apparatus. The particle sizedetermination may also be carried out with methods well-known per se tothe skilled person, based for example on light microscopy, x-raydiffraction, light scattering, such as laser diffractometry. Thecomminution optionally provided as part of the method of the invention,particularly for obtaining uniform particle sizes in the parent startingmaterial, results in better handling and also improved recovery of therespective metal constituents, in particular on the basis of enhanceddigestion of the material and the like.

Furthermore, provision may be made as part of the present invention fordrying of the starting material to be carried out in method step (a)and/or before implementation of method step (b). In this context, thestarting material may be heated to temperatures in the range from 50° C.to 180° C., more particularly 80° C. to 160° C., preferably 100° C. to140° C. It is of advantage in accordance with the invention if thestarting material is adjusted to a residual moisture content of not morethan 5 wt %, more particularly not more than 3 wt %, preferably not morethan 2 wt %, more preferably not more than 1 wt %, based on the driedstarting material. The adjustment of the starting material to a definedresidual moisture content, as defined above, leads in particular to afurther-improved method regime both in terms of the handling of thestarting material and in relation to the chemical reaction processesunderlying the method of the invention.

With further regard to the method of the invention, it is of advantagein accordance with the invention if in method step (b) the oxidationtreatment is carried out as solid phase reaction. The oxidationtreatment ought in particular to be carried out with heating of thestarting material. More particularly the oxidation treatment may becarried out at temperatures in the range from 500° C. to 1000° C., moreparticularly in the range from 600° C. to 900° C., preferably in therange from 650° C. to 950° C. In a manner preferred in accordance withthe invention, the oxidation treatment ought to be carried out usingand/or in the presence of a preferably gaseous oxidizing agent, moreparticularly air and/or oxygen.

In this context, the oxidation treatment may be carried out in generalin the devices suitable for this purpose that are known fundamentally tothe skilled person. More particularly the oxidation treatment may becarried out in an oxidation and/or roasting device. In this context, forexample, the oxidation and/or roasting device may be selected from thegroup of rotary kilns, drum kilns, fluidized bed kilns and entrainedflow reactors.

In particular, in accordance with the invention, it is provided that, inthe oxidation treatment in method step (b), iron is converted at leastsubstantially completely into the trivalent form, more particularly intoiron (III), preferably into iron (III) oxide. In particular, in theoxidation treatment in method step (b), therefore, iron (III) isobtained. Moreover, provision may be made in method step (b), in theoxidation treatment, for iron (II, III) oxide and/or iron (II) oxide tobe converted into iron (III) oxide. In the oxidation treatment in methodstep (b), therefore, an at least substantially complete reaction of thevarious oxidation states and/or oxides of iron in the starting materialto give iron (III) oxide is ensured. In particular, the reaction of therespective iron oxides to give iron (III) oxide may take place inaccordance with the following reaction equation (ii) and/or (iii):2Fe₃O₄+1/2O₂→3Fe₂O₃ and/or  (ii)4FeO+3O₂→2Fe₂O₃  (iii)

The reaction of iron to give iron(III) oxide is carried out inparticular against the background that in accordance with the inventionthere is a downstream or subsequent chlorination provided in order toobtain iron (III) chloride (FeCl₃), which with respect to the regime ofthe invention possesses optimum sublimation properties and henceremoving properties, as observed further below.

In the oxidation treatment in method step (b), there may also beprovision for the further metals as well, especially as defined above,preferably copper, zinc, lead, cobalt, titanium, manganese, vanadiumand/or chromium, more preferably copper, zinc, lead and/or cobalt, andoptionally the noble metal in the form of silver, to be converted intoin each case uniform oxidation states, more particularly into the ineach case highest oxidation state of the metal.

In this context, the product mixture obtained in or after the oxidationtreatment in method step (b) may comprise iron (III) oxide in amounts inthe range from 10 wt % to 95 wt %, more particularly in the range from20 wt % to 90 wt %, preferably in the range from 40 wt % to 85 wt %,based on the dry weight of the product mixture obtained in method step(b). For the purposes of the present invention, therefore, the ironoxides present in the starting material are converted preferably atleast substantially into iron(III) oxide.

As part of the oxidation treatment, there may likewise be provision forthe further metals as well, more particularly copper, zinc, lead and/orcobalt, to be further oxidized, more particularly to give copper(II)oxide, zinc (II) oxide, lead(II) oxide and/or cobalt(II) oxide. This aswell is useful for the subsequent chlorination of these metals. Similarcomments apply in respect of the metals titanium, manganese, vanadiumand chromium.

Provision is made in particular in accordance with the invention,therefore, for the product mixture obtained in the oxidation treatmentin method step (b) to comprise the further metal in the form of themetal oxide, preferably in the form of copper (II) oxide, zinc(II)oxide, lead(II) oxide and cobalt(II) oxide. The product mixture obtainedin the oxidation treatment in method step (b) may in particular comprisesilver oxide. Accordingly there may also, optionally, be a furtheroxidation of the noble metal in the form of silver as part of theoxidation treatment.

Furthermore, the product mixture resulting from the oxidation maycomprise silicon dioxide (SiO₂) and also calcium sulfate (CaSO₄), which,so to speak, each remain at least substantially unchanged in the productmixture.

With regard to the chlorination carried out subsequently as part of themethod of the invention, particularly of the resulting oxides of ironfrom method step (b) and/or the oxides of the further metals resultingin method step (b), and/or, optionally, silver oxide, it is preferred inaccordance with the invention if in method step (c) the chlorination iscarried out as a solid phase reaction.

In this context, in method step (c), the oxidation products obtained inmethod step (b) and/or the product mixture obtained in the oxidationtreatment in method step (b) ought to be brought to temperatures in therange from 100° C. to 320° C., more particularly in the range from 150°C. to 302° C., preferably in the range from 180° C. to 300° C. In methodstep (c), in particular, the chlorination ought to be carried out attemperatures in the range from 100° C. to 320° C., more particularly inthe range from 150° C. to 302° C., preferably in the range from 180° C.to 300° C.

As far as the chlorination as per method step (c) is further concerned,it may be carried out in chlorinating devices well-known per se to theskilled person. In particular, the chlorination in method step (c) maybe carried out in a chlorinating device, in particular where thechlorinating device is selected from the group of rotary kilns and drumkilns.

With further regard to the chlorination, it is especially advantageousin accordance with the invention if the procedure is such that in methodstep (c) iron oxide, more particularly iron(III) oxide, is convertedinto iron chloride, more particularly iron(III) chloride (FeCl₃).

As observed above, the iron(III) chloride or FeCl₃ which results in apreferred way has optimum removing properties in terms of the methodregime of the invention, particularly in respect of the sublimationproperties of iron (III) chloride.

In particular, according to one inventively preferred embodiment,whereby, as observed in detail further below, the chlorinating agentused is ammonium chloride (NH₄Cl), the conversion of iron (III) oxideinto the corresponding chloride may be carried out according to thefollowing reaction equation (iv):Fe₂O₃+6NH₄Cl→2FeCl₃+6NH₃+3H₂O  (iv)

Equally, in accordance with the method regime of the invention, with thechlorination of the metal oxides obtained beforehand and/or present inthe product mixture, provision may be made for copper oxide, preferablycopper(II) oxide, to be converted in method step (c) into copperchloride, more particularly copper (II) chloride (CuCl₂). Equally,provision may be made in method step (c) to convert zinc oxide,preferably zinc(II) oxide into zinc chloride, more particularly zinc(II) chloride (ZnCl₂). Moreover, provision may be made in method step(c) to convert lead oxide, preferably lead(II) oxide into lead chloride,more particularly lead(II) chloride (PbCl₂). Finally, provision may bemade in method step (c) to convert cobalt oxide, preferably cobalt(II)oxide, into cobalt chloride, more particularly cobalt(II) chloride(CoCl₂). Moreover, in method step (c), manganese, particularly manganeseoxide, may be converted into manganese chloride. Equally in method step(c) vanadium, more particularly vanadium oxide, may be converted intovanadium chloride. Finally, in method step (c), chromium, moreparticularly chromium oxide, may be converted into chromium chloride.

Furthermore, in method step (c), silver oxide, preferably silver(I)oxide, may be converted into silver chloride, more particularly silver(I) chloride (AgCl).

As mentioned above, it is preferred in accordance with the invention ifin method step (d) there is removing and/or isolating of iron chloride,more particularly iron(III) chloride (FeCl₃), from the product mixtureobtained in method step (c), specifically by means of an in particularselective sublimation.

In this context it has in accordance with the invention emerged as beingparticularly advantageous if in method step d) the sublimation of ironchloride, more particularly iron (III) chloride, from the productmixture obtained in method step (c) takes place by sublimation, moreparticularly at temperatures in the range from 200° C. to 400° C., moreparticularly in the range from 250° C. to 375° C., preferably in therange from 275° C. to 350° C., more preferably in the range from 300° C.to 325° C.

In this context, the removing or isolating of iron chloride, moreparticularly iron(III) chloride (FeCl₃), may be carried out in aremoving device, more particularly sublimation device, preferably in arotary kiln, fluidized bed kiln and/or drum kiln, into which the productmixture for purification, with the corresponding chlorides, ought to beintroduced beforehand.

According to one inventively preferred embodiment, as part of thepresent invention, a possible procedure adopted, for example, may besuch that method step (c), in other words the chlorination of theoxidation products obtained in method step (b), and method step (d), inother words, in particular, the removing and/or isolating of ironchloride, more particularly iron (III) chloride (FeCl₃), can beaccomplished in particular continuously in a common device, the commondevice being able more particularly to constitute a rotary kiln. In thiscontext, the common device, more particularly the rotary kiln, may havea first section or region for implementation of method step (c), and asecond section or region for implementation of method step (d), moreparticularly for the removing and/or isolating of iron chloride, moreparticularly iron (III) chloride (FeCl₃).

In accordance with this inventive embodiment, therefore, thechlorination on the one hand and the removal of iron chloride on theother may be carried out in one and the same apparatus. As noted above,the joint apparatus is more particularly a rotary kiln, this rotarykiln, along the rotary tube axis, having a first reaction region with afirst temperature zone for implementing the chlorination described inmethod step (c), with the relevant temperatures as provided inaccordance with the invention, and having a second sublimation regionfor the removing of iron chloride, with the corresponding sublimationtemperatures, as described in method step (d).

In accordance with the invention, the desublimation in method step (d)leads, furthermore, in particular to the obtention of solid or purifiediron chloride, more particularly iron(III) chloride (FeCl₃).

Furthermore, the reduction of iron chloride, more particularly iron(III)chloride, optionally carried out in method step d) ought in particularto take place in the gas phase, especially at temperatures in the rangefrom 400° C. to 800° C., more particularly in the range from 450° C. to750° C., preferably in the range from 500° C. to 700° C., morepreferably in the range from 550° C. to 650° C.

The reduction of iron chloride, especially iron(III) chloride, may becarried out in a reduction device. Such reduction devices are well knownfor this purpose to the skilled person, meaning that no furtherobservations are needed in this respect. For this purpose it is possiblein particular for gaseous iron chloride to be transferred from thesublimation device into the reduction device.

With further regard to the method of the invention, provision may alsobe made for there to be a further and/or subsequent removing and/orisolation of the chlorides of the further metals from the productmixture in method step (d), in particular following removing and/orisolating of iron chloride, more particularly iron(III) chloride(FeCl₃).

In particular, in the context of the present invention, provision may bemade for method step (d), especially after removing and/or isolating ofiron chloride, more particularly iron(III) chloride (FeCl₃), has takenplace, to comprise further and/or subsequent removing and/or isolatingof copper chloride, more particularly copper(II) chloride (CuCl₂),and/or of zinc chloride, more particularly zinc (II) chloride (ZnCl₂),and/or of lead chloride, more particularly lead (II) chloride (PbCl₂),and/or of cobalt chloride, more particularly cobalt (II) chloride(CoCl₂). Similar may apply in respect of titanium chloride, manganesechloride, vanadium chloride and/or chromium chloride.

For this purpose, the further or subsequent removing and/or isolating ofchlorides of the further metals from the product mixture may take place,for example, in a slurrying or dispersing device, more particularly in astirred tank and/or stirred reactor, preferably having at least onewithdrawal means, and/or a countercurrent device, preferably having ineach case at least one withdrawal means.

In this context, in accordance with the invention, the procedure may forexample be such that the product mixture freed in particular from ironchloride, preferably iron (III) chloride (FeCl₃), is taken up, moreparticularly slurried and/or dispersed, in a liquid phase and/or in aliquid medium, more particularly water.

In accordance with this aspect of the present invention, the solubleconstituents of the product mixture freed in particular from ironchloride, preferably iron (III) chloride (FeCl₃), especially thechlorides of the further metals, more particularly copper chloride,preferably copper(II) chloride (CuCl₂), and/or zinc chloride, preferablyzinc(II) chloride (ZnCl₂), and/or lead chloride, preferably lead(II)chloride (PbCl₂), and/or cobalt chloride, preferably cobalt(II) chloride(CoCl₂), may in particular be at least substantially completelydissolved and/or suspended, preferably dissolved. In this way, thechlorides in question of the further metals may be removed from theslurried product mixture by transfer into a suspension or solution, witha high rate of removing or purification being achievable by virtue ofthe good solubility or suspendability of the chlorides.

With regard in general to the removing of the chlorides of the furthermetals, it may be carried out on the basis of what is called waterleaching or on the basis of what are called leaching techniques,well-known per se to the skilled person, and hence requiring no furtherobservations.

In accordance with the invention, provision may be made for theresulting solution and/or suspension, preferably solution, comprisingthe chlorides in question to be removed from the remaining productmixture, by means for example of filtration or the like, moreparticularly using corresponding filter devices.

In this context, there may be further work-up of the resulting solutionor suspension, for the especially selective removing or isolating of thechlorides of the further metals, more particularly copper chloride,preferably copper(II) chloride, (CuCl₂), and/or zinc chloride,preferably zinc (II) chloride (ZnCl₂), and/or lead chloride, preferablylead(II) chloride (PbCl₂), and/or cobalt chloride, preferably cobalt(II) chloride (CoCl₂), and/or titanium chloride, and/or manganesechloride, and/or vanadium chloride and/or chromium chloride, or to givethe metallic form of the respective metal. The especially selectiveremoving or isolating of the chlorides of the further metals and/or theconversion to the metallic form of the respective metals may beaccomplished on the basis of electrochemical, sorptive, moreparticularly adsorptive, methods and/or by means of, in particular,selective precipitation and/or, in particular, selective sedimentationor the like. In particular, the metals can be obtained in metallic formby means of reduction. The relevant methods are well-known to theskilled person, and so no further observations are required in thisregard.

With regard, therefore, to the removing or isolating of the chlorides ofthe further metals, a procedure in accordance with the invention isparticularly such that the corresponding metal chlorides are transferredinto solution and/or suspension, preferably into solution, and aretherefore removed from the at least substantially insoluble constituentsof the previously iron-freed product mixture, and the solution orsuspension obtained in this way is subjected to selective removing ofthe chlorides of the further metals.

In this way, in the context of the present invention, it is alsopossible to remove the corresponding chlorides of the further metalsfrom the parent product mixture based on the starting material used, andso in this way, further industrially and/or technically utilizable rawmaterials and/or commercial products can be obtained, which aresuitable, for example, for use as or in catalysts, for producing dyesand/or pigments, or the like, with the raw materials in question, in theform of the chlorides of the further metals, equally possessing a highphysical or product purity.

With regard to the remaining, more particularly at least substantiallyinsoluble product mixture freed from iron and also from the furthermetals, as defined above, this mixture also comprises, in particular,the noble metal components, more particularly gold and/or silver, andalso the constituents silicon, more particularly silicon dioxide, andcalcium sulfate. The remaining product mixture may in particular alsoinclude silver chloride, which is virtually insoluble in water.

As a result of the upstream removing and/or isolating of the ironcomponent and also of the further metal components from the productmixture, there is a further enrichment or further concentration or anincrease in the relative proportion, in particular, of the noble metalsas well, such as gold and/or silver, in the remaining product mixture,and this is beneficial to the subsequently and optionally providedremoval of the noble metals, not least in relation to the economics ofthe parent method and also the degrees of yield.

Hence for the purposes of the present invention, provision may be madefor the product mixture obtained in method step (d), or present aftermethod step (d) has been implemented, to comprise, calculated in eachcase as element and based in each case on the dry weight of the productmixture:

-   -   gold, more particularly in amounts in the range from 1 g/t to 50        g/t, preferably in the range from 1 g/t to 40 g/t, more        preferably in the range from 2 g/t to 20 g/t, very preferably in        the range from 3 g/t to 15 g/t;    -   silver, more particularly in amounts in the range from 2 g/t to        600 g/t, preferably in the range from 5 g/t to 500 g/t, more        preferably in the range from 10 g/t to 400 g/t, very preferably        in the range from 15 g/t to 200 g/t.

In accordance with the invention, for the targeted recovery of the noblemetals enriched beforehand, following method step (d), it is possible tocarry out a method step (e). In method step (e), the noble metal, moreparticularly gold and/or silver, may be removed from the product mixtureobtained in method step (d) and/or from the product mixture freed fromiron chloride, preferably iron(III) chloride (FeCl₃), and from thechlorides of the further metals. High yields can be achieved here aswell on account of the preceding enrichment of the noble metals in theproduct mixture.

With regard to the optionally envisaged removing of the noble metal, apossible procedure, in a manner preferred in accordance with theinvention, is that in method step (e) the noble metal, more particularlygold and/or silver, is removed from the product mixture taken up, moreparticularly slurried and/or dispersed, in a liquid phase and/or in aliquid medium, more particularly water. The removal of the noble metal,more particularly of gold and/or silver, may in particular be carriedout in at least one removing and/or filter device. For this purpose,where necessary, the product mixture obtained in method step (d) mayagain be admixed with a dispersion medium or dissolution medium, moreparticularly water.

In this context it has proved advantageous in accordance with theinvention if in method step (e) the noble metal, more particularly goldand/or silver, is brought or transferred, in particular at leastsubstantially completely, into solution or suspension, more particularlyinto solution. This may be done, for example, by using at least onecomplexing component and/or complexing compound to transfer the noblemetal, more particularly gold and/or silver, into solution and/orsuspension, preferably solution, or contacting it in particular with theproduct mixture and/or with the noble metal.

Generally speaking, the complexing component or compound in question maybe a substance which preferably forms, with the noble metal, moreparticularly gold and/or silver, a complex compound which is at leastsubstantially entirely soluble or suspendable in the dissolution medium,more particularly water.

The complexing component or compound may more particularly be selectedfrom the group of cyanide liquor, iodine/bromine solution andthiosulfate solution. More particularly it is possible to use a solutionof the salt of hydrocyanic acid, more particularly sodium cyanide(NaCN), as a component for transferring the noble metal into a solutionand/or suspension.

Suitable more particularly as a relevant component, as noted above, is asodium cyanide solution, also referred to synonymously as cyanideliquor. The reason is that as part of what is called cyanide leaching,gold and/or silver are dissolved or suspended in a complex compoundcomprising, in particular, oxygen-containing sodium cyanide solution,especially on the basis of the following reaction equation (v):4Au+8NaCN+O₂+2H₂O→4Na[Au(CN)₂]+4NaOH.  (v)

For the noble metal in the form of silver, correspondingly, the validreaction equation is (vi):4Ag+8NaCN+O₂+2H₂O→4Na[Ag(CN)₂]+4NaOH.  (vi)

Subsequently there may further be provision for the resulting solutionand/or suspension of the noble metal, more particularly gold and/orsilver, to be removed from the remaining product mixture, in particularby means of filtration, and for the noble metal, more particularly goldand/or silver, to be recovered from the solution and/or suspension, moreparticularly by means of precipitation methods or sorptive, especiallyadsorptive, methods.

For example, there may be a precipitation of the noble metal using zincand/or aluminum, preferably in finely particulate form, moreparticularly on the basis of the following reaction equations (vii) and(viii):2Na[Au(CN)₂]+Zn→Na₂[Zn(CN)₂]+2Au;  (vii)2Na[Ag(CN)₂]+Zn→Na₂[Zn(CN)₂]+2Ag.  (viii)

The precipitation of the noble metal may be followed by a furtherfiltration and purification of the crude noble metal obtained.

According to a further embodiment of the present invention, it is alsopossible to use sorptive, more particularly adsorptive, purificationmethods in order to obtain the noble metal, based in particular on apreferably particulate adsorption material, more particularly activecarbon. For this purpose it is possible to operate with correspondingadsorption columns or the like. In principle it is also possible toemploy further recovery or purification methods, such as amalgam methodsand/or anode slurry methods, to obtain the noble metal.

On the basis of the method of the invention, therefore, efficientrecovery even of noble metals, such as gold and/or silver, from theparent starting material is possible, with high yield rates beingobtained in this respect, not least under the consideration that thenoble metals in question are already concentrated, so to speak, in theproduct mixture under treatment, as a result of the upstream removal ofthe respective metal components. On the basis of the method of theinvention, very high purities can be obtained even for the purified andisolated noble metals.

In the present invention, moreover, one particular possible approach isthat the product mixture obtained in method step (d) and/or in methodstep (e) further comprises silicon originating from the startingmaterial, more particularly in the form of a silicon oxide, preferablysilicon dioxide. Equally, in the present invention, it may be the casethat the product mixture obtained in method step (d) and/or in methodstep (e) further comprises at least one alkali metal and/or alkalineearth metal originating from the starting material, more particularly atleast one alkaline earth metal, preferably calcium. The alkali metal oralkaline earth metal, more particularly the alkaline earth metal,preferably calcium, may be present in particular in the form of at leastone salt, more particularly sulfate. In particular, the product mixtureobtained in method step (d) or in method step (e) may comprise calciumsulfate originating from the starting material. Indeed, as regards theaforementioned components specifically, they are at least substantiallynot removed from the product mixture or chemically modified, on thebasis of the method steps recited for the purification of the respectivemetal components and/or noble metal constituents, and, consequently,they are present as such at least substantially completely in theremaining product mixture.

In this context, in accordance with the invention, and in relation tothe remaining product mixture, it is possible to envisage in particulara further removing or processing of silicon dioxide. For example,reduction to silicon may take place, based for example on the followingreaction equation (ix):SiO₂+C→Si+CO₂.  (ix)

With regard, furthermore, to the calcium sulfate remaining in theproduct mixture, it may be utilized as such, for the purpose ofproducing gypsum building materials or the like, for example.

In particular, the method of the invention may also be carried out usingthe recovery plant, defined below, according to the invention.

As observed above, the method of the invention is further described bythe relevant co-independent method claims and dependent claims, and alsoby the reference to the corresponding figures.

All in all, therefore, on the basis of the present invention, a highlyefficient method is provided for the purification or isolation, moreparticularly for selective and comprehensive purification or isolation,of metals, especially for the purpose of obtaining metallic iron, andalso further metal components and optionally noble metals, such as goldand silver, more particularly from pyrite cinder, such as roastedpyrites.

According to one particular embodiment of the present invention, apossible procedure is for roasted pyrites previously dried at 120° C. tobe subjected to oxidative roasting at 700° C. with the aim of convertingiron into the trivalent form. Thereafter the oxidized roasted pyritesmay be treated with solid ammonium chloride at a temperature of 300° C.to convert iron into the chloride form, to give ammonia and water in thegas phase. Subsequently, the iron chloride obtained may be removed fromthe product mixture by sublimation. This iron chloride is transferredinto the gas phase, or sublimed, at a temperature of 950° C., withsilicon dioxide and calcium sulfate and also the chlorides of thefurther metals, and the noble metal components, remaining in the solidproduct mixture. The remaining product mixture has an increased noblemetal content by comparison with the starting material. Iron chloridecan subsequently be reduced or treated with hydrogen to give metalliciron and hydrogen chloride gas. The gas streams of ammonia and hydrogenchloride can be combined for renewed formation of ammonium chloride, andreacted. From the product mixture remaining after the removal of ironchloride, the chlorides of the further metals may be transferred intosolution by slurrying and removed. The residual product mixture thusobtained, after removal of the chlorides of the further metals, may betreated with a cyanide solution in order to convert gold and silver intoa soluble form. The residual which remains in the purified productmixture, and which comprises a mixture of silicon dioxide (quartz) andcalcium sulfate (gypsum), can be removed by filtration from the solutioncomprising gold and/or silver. Finally, the noble metal can be obtainedin the form of gold and/or silver by precipitation.

In the text below, the present invention on the basis of the method ofthe invention is elucidated in more detail using preferred workingexamples and figures or drawings that show embodiments. In connectionwith the elucidation of these preferred working examples of the methodof the invention, which, however, are in no way restrictive on themethod of the invention, further advantages, properties, aspects andfeatures of the present invention are also shown.

In the FIGS.

-   -   FIG. 1 shows a schematic representation or overview of the        method of the invention for obtaining raw material from ores or        ore residues, more particularly for recovering metals from ores        or ore residues, preferably for recovering metals from pyrite        residues, more preferably from roasted pyrites obtained in the        production of sulfuric acid;    -   FIG. 2 shows a further schematic representation or overview of        the method of the invention, according to a further inventively        preferred embodiment.

FIG. 1 schematizes one particular embodiment of the method of theinvention, as will be further defined below.

In particular, FIG. 1 shows the regime of the invention, whereby firstof all a raw material RM is present or is provided, this material moreparticularly being an ore or an ore residue, more particularly a pyriteresidue or, in particular, roasted pyrites originating from sulfuricacid production. The raw material RM comprises, in particular, iron,preferably as main constituent, and at least one noble metal, moreparticularly gold and/or silver, and also at least one further metal,preferably selected from the group of copper, zinc, lead and cobalt,with, in particular, iron and also the further metal being present inthe form of oxides.

In method step (a) there is a provision, more particularly processing,of a starting material AM on the basis of the parent raw material RM.The processing may comprise comminution of the raw material RM and/ordrying of the raw material RM to give the processed starting materialAM.

After that, the starting material AM, as shown in FIG. 1, is subjectedas per method step (b) to an oxidation treatment, which may be carriedout in particular as calcining or oxidative roasting. In this context,an oxidizing agent, such as air and/or oxygen, may in particular beused. This results in a material OP with corresponding oxidationproducts, the oxidation products comprising, in particular, iron oxideand optionally oxides of the further metals. Particularly in relation toiron oxide, iron (III) oxide is obtained in this context.

FIG. 1 further shows that in a further method step (c) there is achlorination of the oxidation products, more particularly oxides,obtained in method step (b), resulting correspondingly in chlorinatedproducts CP. The chlorination of the oxides may take place by means of arecyclable chlorinating agent, especially ammonium chloride (NH₄Cl). Theresult on the one hand, starting from iron(III) oxide, iscorrespondingly iron(III) chloride (FeCl₃), and, starting from thefurther metal oxides, corresponding chlorides of the further metals(Me_(x)-Cl_(y)) where Me=Cu, Zn, Pb, Co, Ti, V or Cr, more particularlyCu, Zn, Pb or Co).

The chlorinated products CP obtained by the chlorination may then beremoved or isolated from the product mixture obtained in method step(c), as illustrated by FIG. 1 in accordance with the method step (d)recited therein. In particular, the iron (III) chloride (FeCl₃) obtainedbeforehand in method step (c) is sublimed in method step (d), givinggaseous iron(III) chloride (FeCl₃) (g)), which may be removedaccordingly from the solid residual mixture or residue.

In this context, FIG. 1 further shows that the resulting, especiallygaseous iron (III) chloride can be desublimed on the one hand, to givesolid iron(III) chloride, and that, on the other hand, the especiallygaseous iron (III) chloride can be subjected to reduction to givemetallic iron (Fe). The reaction products arising during the reductionof iron (III) chloride to metallic iron, especially in the form of aninorganic chlorine compound, preferably hydrogen chloride, may be usedfor the recycling of the chlorinating agent, as illustrated alsoschematically in FIG. 1, with the inorganic chlorine compound obtainedfrom the reduction, preferably hydrogen chloride, being reacted withreaction product resulting from the chlorinating agent in thechlorination, more particularly with gaseous ammonia (NH₃), so that inthis way the chlorinating agent is obtained again in the form ofammonium chloride (NH₄Cl) which can be used again in method step (c).

FIG. 1 shows, furthermore, that in method step (d) there may also besubsequent removal of the chlorides of the further metals(Me_(x)Cl_(y)), in particular downstream of the removal of iron(III)chloride. Method step (d) results in a remaining product mixture (VP),which optionally, in method step (e), as also illustrated in FIG. 1, maybe supplied to a further purification procedure, particularly inrelation to the removal of noble metals, such as gold and/or silver. Thesolid product mixture remaining in method step (e) and freed from goldand/or silver comprises, in particular, calcium sulfate and silicondioxide, and silicon dioxide, as recited in FIG. 1, can be subjected toreduction to give elemental silicon.

FIG. 2 schematizes one further particular embodiment of the method ofthe invention, as further described below:

Accordingly, as set out in FIG. 2, starting from a raw material such as,in particular, roasted pyrites, comprising components based on iron,copper, zinc, cobalt, gold, silver, lead, silicon and calcium, and alsobased on further elements, a processed starting material may be obtainedby drying and comminuting.

The resulting starting material may be subjected to oxidation orcalcining, at temperatures, for example, of 700° C., in the presence ofan oxidizing agent, such as air and/or oxygen. The oxidizing treatmentleads in particular to oxides of iron and of the further metals beingobtained, also in particular with an increase in the oxidation state ofthe respective metallic elements. Thus in the case of iron, for example,starting from iron (II) oxide or iron (II, III) oxide, iron(III) oxideis obtained fundamentally, in accordance with the following reactionscheme:4FeO+3O2→2Fe₂O₃.  (x)

Equally, starting for example from copper (I) oxide, copper (II) oxideis obtained fundamentally, in accordance with the following reactionscheme:2Cu₂O+O₂→4CuO.  (xi)

Similar comments apply generally in respect of the elements of thefurther metals.

With regard furthermore to the noble metal, especially gold, it isgenerally not oxidized as part of the oxidation treatment, owing to itsnoble properties. For silver as the noble metal, there may be at leastpartial conversion into the oxide.

FIG. 2 illustrates, furthermore, by way of example, the chlorination,following the oxidation, of the oxidation products obtained beforehand,using a chlorinating agent in the form of ammonium chloride (NH₄Cl),which can be added to the oxidation products in solid form, in the formof a powder, for example. The chlorination may take place for example attemperatures of 300° C. The result in relation to iron(III) oxide,correspondingly, is iron (III) chloride (FeCl₃) and also, purely by wayof example, the result for copper oxide, correspondingly, is copperchloride (CuCl₂). Similar comments apply in respect of the oxides of thefurther metals. In the chlorination that is carried out, especiallygaseous ammonia (NH₃) may result as a reaction product originating fromthe chlorinating agent, especially ammonium chloride (NH₄Cl).

FIG. 2 further illustrates in this context how the resulting, inparticular gaseous, ammonia (NH₃) can be taken off and reacted in thegas phase with an inorganic chlorine compound, more particularlyhydrogen chloride, to give recycled chlorinating agent, moreparticularly ammonium chloride (NH₄Cl).

With regard to the further procedure, the resulting chlorinatingproducts, especially iron chloride and optionally the chlorides of thefurther metals, are removed from the product mixture obtained in thechlorination: hence FIG. 2 further illustrates how iron(III) chloride(FeCl₃) are transferred into the gas phase by sublimation, moreparticularly at temperatures of 350° C., and so removed from the productmixture.

After sublimation and/or removal of iron(III) chloride, it is possible,as shown in FIG. 2, for the chlorides of the further metals, such asCuCl₂, ZnCl₂, CoCl₂, PbCl₂, etc., also to be removed subsequently fromthe product mixture, in particular by slurrying and/or dispersing of theproduct mixture freed from iron (III) chloride, with correspondingtransfer of soluble chlorides into a solution, more particularly aqueoussolution, with subsequent removal of the solution, for example by meansof filtration.

With regard, furthermore, to the iron (III) chloride present as a resultof sublimation and present, in particular, in the gaseous state, themethod of the invention allows the operation to take place on the basisof two different variants or embodiments, as shown in FIG. 2: on the onehand, the iron(III) chloride, more particularly in gaseous form, may bedesublimed by desublimation to solid iron (III) chloride, to give thecorresponding end product. On the other hand, iron(III) chloride, moreparticularly gaseous iron(III) chloride, may be subjected to reduction,in particular at 600° C., and hydrogen, for example, may be used asreducing agent. The reduction may take place in particular in accordancewith the following chemical reaction equation: 2 FeCl₃+3 H₂→2 Fe+6 HCl.In this way, metallic iron is obtained. In the context of the presentinvention it is equally possible for both above-recited embodiments tobe realized simultaneously or in parallel, for example by correspondingtreatments of corresponding component streams of iron chloride.

FIG. 2 further illustrates how hydrogen chloride obtained during thereduction of iron(III) chloride can be taken off and used for therecycling of the above-recited chlorinating agent.

With regard, furthermore, to the product mixture freed from thechlorides of the aforementioned metals, it is equally possible for thenoble metal, more particularly gold and/or silver, to be removed, asshown in FIG. 2: for example, the noble metals, such as gold and/orsilver, may be converted into solution or suspension, more particularlyaqueous solution or suspension, by means in particular of a complexingreaction, through the use of a corresponding cyanide liquor, forexample. The underlying complex-forming reaction to give, in particular,water-soluble noble metal may be run on the basis of the subsequentreaction equation: Em+8 NaCN+O₂+2 H₂O→4 Na[Em(CN)₂]+4 NaOH; Em=Au or Ag.

FIG. 2 further illustrates how the noble metals transferred intosolution or suspension, especially gold and/or silver, can be purifiedfurther by corresponding filtration or removal of the solidconstituents, to give a purified noble metal solution or noble metalsuspension. From this solution or suspension, the isolated noble metal,more particularly gold and/or silver, may be attained by means ofextraction or extractive precipitation or adsorption. In this context,FIG. 2 shows, by way of example, the underlying reaction using aprecipitant such as zinc or aluminum: 2 Na[Em(CN)₂]+Fm→Na₂[Fm(CN)₂]+2Em; Em=Au or Ag and also Fm=precipitant (Zn or Al).

With regard, furthermore, to the product mixture which remains, itcomprises, in particular, calcium sulfate and also silicon dioxide;silicon dioxide can be converted into silicon by a correspondingreduction, using carbon as reactant, for example, as also shown in FIG.2.

Furthermore, the present invention—according to a further aspect of thepresent invention—relates to the recovery plant of the invention,particularly for obtaining/recovering metallic iron and/or ironcompounds, more particularly iron chloride, from ores and/or oreresidues, preferably from pyrite residues, very preferably from roastedpyrites obtained in the production of sulfuric acid, more particularly arecovery plant for implementing the method defined above, where therecovery plant comprises:

-   -   (a) at least one providing and/or processing device, more        particularly for the providing, more particularly processing, of        a starting material in the form of at least one ore and/or ore        residue, more particularly of at least one pyrite residue,        preferably of one or more roasted pyrites obtained in the        production of sulfuric acid, in particular where the starting        material comprises iron, at least one noble metal and at least        one further metal;    -   (b) at least one oxidation and/or roasting device, more        particularly for the oxidation treatment, more particularly        calcining and/or oxidative roasting, of the provided starting        material, more particularly to give iron oxide and oxides of the        further metals as oxidation products in the resulting product        mixture;    -   (c) at least one chlorinating device, more particularly for the        chlorination of the oxidation products, more particularly        oxides, in the product mixture and/or for the use of at least        one chlorinating agent, more particularly recyclable        chlorinating agent, preferably for the chlorination of iron        oxide and optionally oxides of the further metals, more        particularly to give iron chloride, preferably iron (III)        chloride, and optionally chlorides of the further metals in the        product mixture;    -   (d) at least one removing device, especially for selectively        removing and/or isolating iron chloride, preferably iron (III)        chloride, from the product mixture, where the removing device is        designed as a sublimation device,        -   where the recovery plant, in particular after and/or            downstream in the process direction of the removing device,            has at least one desublimation device, especially for            receiving and desubliming of, in particular, sublimed iron            chloride and/or for obtaining, in particular, solid and/or            purified iron chloride, in particular where the            desublimation device is connected to the removing device, or        -   where the recovery plant, in particular after and/or            downstream in the process direction of the removing device,            has at least one reduction device, more particularly for            reducing, in particular, sublimed iron chloride, more            particularly iron (III) chloride (FeCl₃), and for obtaining            metallic iron and/or for obtaining at least one inorganic            chlorine compound, more particularly hydrogen chloride            (HCl), in particular where the reduction device is connected            to the removing device;            where the above-stated devices, namely the providing and/or            readying device, the oxidation and/or roasting device, the            chlorinating device, and the removing device, are arranged            downstream of one another in the process direction, in the            order stated, and where the further above-stated devices,            namely the desublimation device and the reduction device,            are arranged as defined above.

The recovery plant of the invention is particularly suitable for use inthe context of the above-described method according to the invention. Inparticular, the recovery plant of the invention enables on the one handan efficient and comprehensive purification or removal of the metalliccomponents from the parent starting material, and in this context, inparticular, iron can be obtained both in metallic form, as a rawmaterial for further use, more particularly further industrial use, andin the form of iron chloride, more particularly iron(III) chloride. Inaddition, on the basis of the recovery plant of the invention, noblemetals, in the form of gold and silver, can be obtained. Furthermore,the recovery plant of the invention permits the recycling of thechlorinating agent, envisaged in particular in relation to the method ofthe invention, which is accompanied by the corresponding economic andenvironmental advantages.

For the purposes of the present invention there may also be provisionfor the recovery plant of the invention to have at least onedesublimation device and at least one reduction device, each asdescribed above, especially when simultaneous or parallel recovery bothof iron chloride and of metallic iron is to be carried out, inparticular on the basis of the treatment of corresponding sub-streamsof, in particular, sublimed iron chloride.

For further observations in this regard, in respect of the recoveryplant according to the invention, reference may be made to the dependentclaims relating to the purification plant of the invention, and to thecorresponding figures.

The present invention will now be particularized in more detail inrelation to the recovery plant of the invention, using preferred workingexamples and drawings and figures that show embodiments. In connectionwith the elucidation of these preferred working examples of the presentinvention, which, however, are in no way restrictive in relation to thepresent invention, further advantages, properties, aspects and featuresof the present invention will also be shown.

In the further FIGS.:

-   -   FIG. 3 shows a schematic representation or overview of the        recovery plant A of the invention, preferably for obtaining raw        material from ores or ore residues, more particularly for        recovering metals from ores or ore residues, preferably for        recovering metals from pyrite residues, more preferably from        roasted pyrites obtained in sulfuric acid production;    -   FIG. 4 shows a further schematic representation or overview of        the recovery plant A of the invention, in accordance with a        further inventive embodiment.

FIG. 3 and FIG. 4 therefore schematize preferred embodiments of therecovery plant A of the invention, as will be further defined below:

In particular, FIG. 3 and FIG. 4 show the recovery plant A of theinvention, in particular for obtaining/recovering metallic iron and/oriron compounds, more particularly iron chloride, from ores and/or oreresidues, preferably from pyrite residues, very preferably from roastedpyrites obtained in the production of sulfuric acid, more particularly arecovery plant A for implementing the above-defined method in accordancewith the invention, where the recovery plant A comprises:

-   -   (a) at least one providing and/or processing device 1, more        particularly for the providing, more particularly processing, of        a starting material in the form of at least one ore and/or ore        residue, more particularly of at least one pyrite residue,        preferably of one or more roasted pyrites obtained in the        production of sulfuric acid, in particular where the starting        material comprises iron, at least one noble metal and at least        one further metal;    -   (b) at least one oxidation and/or roasting device 2, more        particularly for the oxidation treatment, more particularly        calcining and/or oxidative roasting, of the provided starting        material, more particularly to give iron oxide and oxides of the        further metals as oxidation products in the resulting product        mixture;    -   (c) at least one chlorinating device 3, more particularly for        the chlorination of the oxidation products, more particularly        oxides, in the product mixture and/or for the use of at least        one chlorinating agent, more particularly recyclable        chlorinating agent, preferably for the chlorination of iron        oxide and optionally oxides of the further metals, more        particularly to give iron chloride, preferably iron (III)        chloride, and optionally chlorides of the further metals in the        product mixture;    -   (d) at least one removing device 4, especially for selectively        removing and/or isolating iron chloride, preferably iron (III)        chloride, from the product mixture, the removing device 4 being        designed as a sublimation device,        -   where the recovery plant A, in particular after and/or            downstream in the process direction of the removing device            4, has at least one desublimation device 14, more            particularly for receiving and desubliming, in particular,            sublimed iron chloride and/or for obtaining, in particular,            solid and/or purified iron chloride, in particular where the            desublimation device 14 is connected to the removing device            4 (the latter in particular for receiving, in particular,            gaseous iron chloride from the removing device 4), or        -   where the recovery plant A, in particular after and/or            downstream in the process direction of the removing device            4, has at least one reduction device 15, in particular for            reducing, in particular, sublimed iron chloride, more            particularly iron(III) chloride (FeCl₃), and for obtaining            metallic iron and/or for obtaining at least one inorganic            chlorine compound, in particular hydrogen chloride (HCl), in            particular where the reduction device 15 is connected to the            removing device 4 (the latter in particular for receiving,            in particular, gaseous iron chloride from the removing            device 4);

where the above-stated apparatus 1, 2, 3, 4 are arranged in the orderindicated downstream of one another in the operating direction and wherethe above-stated apparatus 14, 15 are arranged as defined above.

The chlorinating device 3 may be selected in accordance with theinvention from the group of rotary kilns and drum kilns.

As can be seen from FIG. 4, the chlorinating device 3 have at least onesupply means 8 for the supply of a chlorinating agent, especiallyammonium chloride (Na4Cl). Moreover, the chlorinating device 3 may haveat least one takeoff and/or removal means 9, in particular for therecovery and/or removing of reaction products resulting from thechlorinating agent in the chlorination of the oxidation products, moreparticularly of preferably gaseous ammonia (NH₃).

Furthermore, it is also apparent from FIG. 3 and FIG. 4 the recoveryplant A can have at least one reaction and/or condensation device 10.The reaction and/or condensation device is used in particular forcombining or contacting and for the reaction of in particular gaseousammonia (NH₃) on the one hand and on the other hand of at least onepreferably inorganic chlorine compound, especially hydrogen chloride(HCl), in order to give recycled chlorinating agent, preferably ammoniumchloride (NH₄Cl).

The reaction and/or condensation device 10 may be connected inparticular to the chlorinating device 3, in particular such that,preferably independently of one another, gaseous ammonia can be guidedfrom the chlorinating device 3 into the reaction and/or condensationmeans 10, and recycled ammonium chloride can be guided from the reactionand/or condensation means 10 into the chlorinating device 3. Moreover,the reduction device 15 may be connected to the reaction and/orcondensation device 10, especially for delivering an inorganic chlorinecompound, more particularly hydrogen chloride (HCl), from the reductiondevice 15 into the reaction and/or condensation device 10.

On the basis of the apparatus-related peculiarity of the deliberate useof a reaction or condensation device 10, therefore, the recovery plant Aof the invention permits the recycling of the chlorinating agent, namelymore particularly of ammonium chloride.

In general, the reaction or condensation device 10, as schematized inFIG. 3, is able to receive an inorganic chlorine compound, resulting inconnection with the reduction of iron chloride removed from the productmixture in the removing device 4, and this chlorine compound is used forthe recycling of the chlorinating agent.

With regard specifically to the reaction or condensation device 10,provision may be made in accordance with the invention for this device,as shown in FIG. 4, to have a supply means 11 for supplying and/orreceiving especially gaseous ammonia (NH₃), and/or at least one furthersupply means 12 for supplying and/or receiving at least one preferablyinorganic chlorine compound, especially hydrogen chloride (HCl), and/orat least one takeoff and/or removal means 13, more particularly forrecovering and/or removing the recycled chlorinating agent, moreparticularly ammonium chloride (NH₄Cl). It is of advantage in accordancewith the invention here if the supply means 11 is connected to thetakeoff and/or removal means 9 of the chlorinating device 3. It isequally an advantage if the takeoff and/or removal means 13 is connectedto the supply means 8 of the chlorinating device 3. In this way, themass transport of the products and reactants that are relevant to thechlorinating agent is made more efficient and more selective.

Furthermore, FIG. 4 shows that the recovery plant A further has at leastone desublimation device 14, more particularly for receiving anddesubliming, in particular, sublimed iron chloride, more particularlyiron(III) chloride (FeCl₃), and/or for obtaining, in particular, solidor purified iron chloride, more particularly iron(III) chloride (FeCl₃).This desublimation device 14 is connected to the removing device 4, moreparticularly to the means 25 of the removing device 4 for the removal ortakeoff of, in particular, gaseous iron chloride, more particularly iron(III) chloride (FeCl₃). In this connection, the desublimation device 14ought to have at least one supply means 19, more particularly forreceiving, in particular, sublimed iron chloride, especially iron(III)chloride (FeCl₃), preferably from the removing device 4.

The desublimation device may be designed, for example, as a coolingand/or condensation device.

FIG. 4 further shows that the plant A in accordance with the inventionalso has at least one reduction device 15, more particularly forreducing, in particular, sublimed iron chloride, more particularly iron(III) chloride (FeCl₃), and for obtaining metallic iron. In thisconnection, the reduction device 15 is connected to the removing device4. Furthermore, the reduction device 15 ought to have at least onesupply means 16, more particularly for receiving, in particular,sublimed iron chloride, especially iron (III) chloride (FeCl₃),preferably from the removing device 4.

As observed above, the reduction device 15 may in particular beconnected to the removing device 4, more particularly for receiving ironchloride. The reduction device 15 in this case is preferably connectedvia the supply means 16 to the means 25 for the removal and/or takeoffof, in particular, sublimed iron chloride, more particularly iron (III)chloride (FeCl₃).

With further regard to the reduction device 15, it may have at least onefurther supply means 17 for supplying and/or receiving a reducing agent,more particularly hydrogen or natural gas (especially methane).

In particular, moreover, the reduction device 15 may be connected to thereaction and/or condensation device 10, in particular for delivering aninorganic chlorine compound, more particularly hydrogen chloride, thatis produced in the course of the reduction of iron chloride, and forreceiving it into the reaction and/or condensation device. In thisconnection, the reduction device 15 may have at least one withdrawaland/or exporting means 18, especially for recovering and/or removing atleast one inorganic chlorine compound, especially hydrogen chloride(HCl), formed in the reduction of iron chloride, especially iron (III)chloride, and/or for taking off at least one inorganic chlorinecompound, more particularly hydrogen chloride (HCl), formed in thereduction of iron chloride, more particularly iron (III) chloride. Inparticular, the takeoff means 18 ought to be connected to the supplymeans 12 of the reaction or condensation device 10.

In this way, the inorganic chlorine compound that is needed for therecycling of the chlorinating agent may be provided via the reduction ofiron chloride from the very procedure on which the recovery plant isbased, and may be transferred, with the recovery plant A of theinvention providing the constructional requirements in this respect, asobserved above.

As indicated in detail in FIG. 4, the providing and/or processing device1 may furthermore and, more particularly with regard to the provision ofthe starting material, comprise at least one comminuting means 6, moreparticularly for comminuting and/or homogenizing the starting material,and/or at least one drying means 7, more particularly for drying thestarting material. According to one inventively preferred embodiment,the drying means 7 here may be arranged in operational directiondownstream of the comminuting means 6.

With further regard to the inventive recovery plant A, the oxidation orroasting device 2 may be selected from the group of rotary kilns, drumkilns, fluidized bed kilns and entrained flow reactors. In particularthe oxidation and/or roasting device 2 may have at least one means forthe supply of at least one oxidizing agent, more particularly air and/oroxygen.

With further regard to the inventive recovery plant A, the removingdevice 4 is designed as a sublimation device. In particular, theremoving device 4 may be a rotary kiln, fluidized bed kiln and/or drumkiln. The removing device ought also to have at least one means 25 forthe withdrawal or takeoff of, in particular, gaseous iron chloride, moreparticularly iron(III) chloride.

FIG. 4 further illustrates an inventive embodiment whereby thechlorinating device 3 and the removing device 4 can be combined into acommon device 24.

In this connection, the common device 24 may be designed in the form ofa common rotary kiln, in particular having at least two, preferably two,temperature sections. In the first temperature section or in the firsttemperature zone, in particular, the temperature may be that needed forthe chlorination of the metal components, and the chlorination of themetal components in the material with the oxidation products obtainedbeforehand may take place by addition of the chlorinating agent; theresulting product mixture with the chlorinated metal components maysubsequently be transferred into the second temperature section or intothe second temperature zone, where, in the second temperature section orin the second temperature zone, the temperatures present may be thoserequired for the sublimation in particular of iron(III) chloride. Inthis connection, the common device 24 ought to have the correspondingmeans for the supply of the chlorinating agent and also for the takeoffof reaction products resulting from the chlorinating agent in thechlorination, more particularly ammonia (NH3), and ought also to have atleast one further means 25 for the withdrawal or takeoff of, inparticular, gaseous iron chloride, more particularly iron(III) chloride(FeCl₃), as it results during the sublimation.

FIG. 4 shows a further embodiment of the inventive plant A, whereby theplant A further has at least one slurrying or dispersing device 20, moreparticularly for removing and/or isolating copper chloride, especiallycopper(II) chloride (CuCl₂), and/or zinc chloride, especially zinc (II)chloride (ZnCl₂), and/or lead chloride, especially lead(II) chloride(PbCl₂), and/or cobalt chloride, especially cobalt(II) chloride (CoCl₂),from the product mixture freed from iron chloride, more particularlyiron (III) chloride (FeCl₃).

In this context, the slurrying or dispersing device 20 to be arranged inoperational direction downstream from the removing device 4 and/or inoperational direction upstream from the removing or filter device 5. Thepurpose in particular of the slurrying or dispersing device 20 is toslurry or disperse the product mixture freed from iron chloride,especially iron (III) chloride (FeCl₃), with the aforementionedchlorides of the further metals being converted into a solution or intoa suspension. In this regard, the slurrying or dispersing device 20 mayalso have at least one means 26 for receiving a dispersion ordissolution and/or suspension medium, more particularly water, servingboth to slurry the product mixture and to convert the relevant chloridesof the further metals into a solution or suspension. Furthermore, theslurrying or dispersing device 20 to have at least one withdrawal means27 for removing the preferably aqueous solution or suspension of thechlorides of the further metals.

In particular, the slurrying and/or dispersing device 20 may be astirred tank or a stirred reactor or a countercurrent device, preferablyhaving in each case at least one withdrawal means 27. The withdrawalmeans are used in particular for removing the preferably aqueoussolution or suspension of the chlorides of the further metals, removedfrom the product mixture.

FIG. 4 further shows an inventive embodiment whereby the plant A alsohas at least one adding and/or supplying device 21, preferably with anadding means 22, more particularly for adding at least one complexingcomponent for converting the noble metal, more particularly gold and/orsilver, into a solution and/or suspension, preferably solution. In thisconnection, the complexing component may be selected from the group ofcyanide liquor, iodine/bromine solution and thiosulfate solution.

As far as the adding device 21 is concerned, it ought to be arranged inoperational direction downstream from the removing device 4, moreparticularly in operational direction downstream from the slurryingand/or dispersing device 20, and/or in operational direction upstreamfrom the removing and/or filter device 5. The purpose of the adding orsupplying device 21 is in particular to receive the product mixturefreed from iron chloride, especially iron(III) chloride and also fromthe chlorides of the further metals.

In the adding or supplying device 21, by addition of the above-definedcomponent, the noble metal present in the product mixture, moreparticularly gold and/or silver, is converted into a solution orsuspension, and in this respect water in particular is used asdissolution or suspension medium. In this connection, the adding orsupplying device 21 may optionally also have at least one means forreceiving the dissolution or suspension medium, more particularly water.

The purpose of the adding or supplying device 21 is therefore inparticular for adding and/or for contacting the component for convertingthe noble metal into a solution and/or dispersion to or with the productmixture, in particular the slurried or dispersed product mixture, whichhas been freed from iron chloride, especially iron (III) chloride, andalso from the chlorides of the further metals.

For example, the adding and supplying device 21 may be a stirred tank orthe like.

Furthermore, the inventive plant A may also have at least one extractiondevice 23, more particularly for removing and/or obtaining the noblemetal, more particularly gold and/or silver, from the solution and/orsuspension. In this connection, the extraction device may be aprecipitating device and/or sorption device, more particularlyadsorption device.

In particular, the extraction device 23 may be arranged in operationaldirection downstream of the removing and/or filter device 5.

For example, the extraction device 23 may be designed such that it hasat least one means 28 for receiving a precipitant such as, inparticular, particulate zinc or aluminum. The gold precipitated in thisway can be removed and isolated via corresponding filter devices orsedimentation devices.

For the removal of the noble metal, it is also possible in general touse stirring devices, thickening devices and filtering devices, basedfor example on drum filters, more particularly drum vacuum filters.

The respective device or means of the recovery plant A of the inventionmay be connected to one another in order to ensure the underlying masstransport or material transport processes, via transport means that areknown per se to the skilled person, based for example on conveyingand/or belt transport means for transporting materials that are presentin solid phase, and/or pipeline means for transporting substances thatare in the gas phase.

Furthermore, the recovery plant of the invention may optionally have atleast one further device for the further processing of the, inparticular, solid product mixture that remains after the removal of thenoble metal, more particularly gold and/or silver. More particularly,the plant of the invention may have at least one device for removingsilicon dioxide and/or at least one device for reducing silicon dioxideto give elemental silicon.

Overall, in the present invention, with the recovery plant A accordingto the invention, an efficient system is provided for the processingespecially of pyrite cinder, such as roasted pyrites, this systemallowing the selective removal or isolation of different raw materialswith economic-industrial relevance. In particular, the recovery plant Aof the invention permits efficient implementation of the methodaccording to the invention, especially in relation to recycling of thechlorinating agent, with reduced use of chemicals and energy overall.

The present invention relates in particular as well to a recovery plantA, preferably as defined above, more particularly forobtaining/recovering metallic iron and/or iron compounds, moreparticularly iron chloride, from ores and/or ore residues, preferablyfrom pyrite residues, very preferably from roasted pyrites obtained inthe production of sulfuric acid, more particularly a recovery plant Afor implementing the method in accordance with the invention and definedabove, where the recovery plant A comprises:

-   -   (a) at least one providing and/or processing device 1, more        particularly for the providing, more particularly processing, of        a starting material in the form of at least one ore and/or ore        residue, more particularly of at least one pyrite residue,        preferably of one or more roasted pyrites obtained in the        production of sulfuric acid, in particular where the starting        material comprises iron, at least one noble metal and at least        one further metal;    -   (b) at least one oxidation and/or roasting device 2, more        particularly for the oxidation treatment, more particularly        calcining and/or oxidative roasting, of the provided starting        material, more particularly to give iron oxide and oxides of the        further metals as oxidation products in the resulting product        mixture;    -   (c) at least one chlorinating device 3, more particularly for        the chlorination of the oxidation products, more particularly        oxides, in the product mixture and/or for the use of at least        one chlorinating agent, more particularly recyclable        chlorinating agent, preferably for the chlorination of iron and        optionally of the further metals, more particularly to give iron        chloride, preferably iron (III) chloride, and optionally        chlorides of the further metals in the product mixture,        -   where the recovery plant A has at least one reaction and/or            condensation device 10, more particularly for combining            and/or contacting and for reacting, in particular, gaseous            ammonia (NH₃) on the one hand and at least one preferably            inorganic chloride compound, more particularly hydrogen            chloride (HCl), on the other hand, to give recycled            chlorinating agent, preferably ammonium chloride (NH₄Cl), in            particular where the reaction and/or condensation device 10            is connected to the chlorinating apparatus 3 (the latter in            particular for receiving ammonia (NH₃) from the chlorinating            device 3 and in particular for delivering recycled            chlorinating agent, more particularly ammonium chloride,            into the chlorinating device 3);    -   (d) at least one removing device 4, more particularly for the        selective removing and/or isolating of iron chloride, preferably        iron (III) chloride, from the product mixture, where the        removing device (4) is designed as sublimation device,        -   where the recovery plant A, more particularly subsequent to            and/or in operating direction downstream of the removing            device 4, has at least one desublimation device 14, more            particularly for receiving and desubliming iron chloride,            more particularly sublimed iron chloride, and/or to give, in            particular, solid and/or purified iron chloride, in            particular when the desublimation device 14 is connected to            the removing device 4 latter in particular for receiving, in            particular, gaseous iron chloride from the removing device            4) or        -   where the recovery plant A, more particularly subsequent to            and/or in operating direction downstream of the removing            device 4, has at least one reduction device 15, more            particularly for reducing iron chloride, more particularly            sublimed iron chloride, more particularly iron(III) chloride            (FeCl₃), and to give metallic iron and/or to give at least            one inorganic chlorine compound, more particularly hydrogen            chloride (HCl), in particular where the reduction device 15            is connected to the removing device 4 (the latter in            particular for receiving, in particular, gaseous iron            chloride from the removing device 4), and/or in particular            where the reduction device 15 is connected to the reaction            and/or condensation device 10; (the latter in particular for            delivering at least one inorganic chlorine compound into the            reaction and/or condensation device 10);    -   (e) optionally at least one slurrying and/or dispersing device        20, especially for subsequent removing and/or isolation of        chlorides of the further metals, more particularly of copper        chloride, more particularly of copper (II) chloride (CuCl₂),        and/or zinc chloride, more particularly zinc (II) chloride        (ZnCl₂), and/or lead chloride, more particularly lead(II)        chloride (PbCl₂), and/or cobalt chloride, more particularly        cobalt (II) chloride (CoCl₂), from the product mixture freed        from iron chloride, more particularly iron (III) chloride        (FeCl₃);

where the above-stated apparatus 1, 2, 3, 4, 20 are arranged in theorder indicated downstream of one another in the operating direction,and where the above-stated devices 10, 14, 15 are arranged as definedabove.

Lastly, the present invention—according to a further aspect of thepresent invention—relates to the use of a recovery plant A, moreparticularly as defined above, in a method for obtaining/recoveringmetallic iron and/or iron compounds, more particularly iron chloride,from ores and/or ore residues, preferably from pyrite residues, morepreferably from roasted pyrites obtained in the production of sulfuricacid, more particularly as defined above.

Further refinements, adaptations, variations, modifications,peculiarities and advantages of the present invention are readilyperceptible and realizable for the skilled person on reading thedescription, without departing the scope of the present invention.

The present invention is illustrated using the exemplary embodimenthereinafter, which is not, however, intended in any way to restrict thepresent invention.

WORKING EXAMPLE

Implementation of the Method of the Invention According to One PreferredEmbodiment of the Present Invention

The method of the invention may be carried out, according to onespecific embodiment of the present invention, as described hereinafter:

1. Provision of the Raw Material

-   -   Raw material used is a pyrite residue in the form of roasted        pyrites originating from sulfuric acid production, in a quantity        of 1000 kg. The raw material used is first subjected to drying        at 120° C. A sample of the raw material is analyzed using a mass        spectrometer with inductively coupled plasma (ICP; ELAN model        DRC) for its elemental composition. The starting material        comprises the following elemental constituents, the        corresponding mass fractions being based on the respective        element:

Element Mass fraction Fe 52 wt % Au 2 g/t Ag 10 g/t Cu 0.2 wt % Zn 0.4wt % Pb 0.04 wt % Co 0.01 wt % Si 7 wt % Ca 4.4 wt %

-   -   A further analysis of the starting material used shows that 65%        of the iron is present in the form of iron (II, III) oxide        (Fe₃CO₄) and 35% of the iron in the form of iron (II) oxide        (Fe₂O₃). Moreover, silicon is present in the form of silicon        oxide, and calcium in the form of calcium sulfate. The further        metals, apart from gold, are in the form of their oxides.    -   The starting material obtained by drying is further processed as        follows:        2. Oxidation Treatment of the Starting Material    -   The dried starting material is subsequently subjected to an        oxidation treatment or calcining (oxidative roasting). For this        purpose, the starting material is heated to a temperature of        700° C. The roasting, in particular, converts iron into the        trivalent form, to give iron (III) oxide (Fe₂O₃). The product        mixture obtained is further analyzed for its composition. The        product mixture obtained after the oxidation treatment comprises        iron now at least substantially completely in the form of        iron (III) oxide (Fe₂O₃). The remaining metals, apart from gold        and calcium, are in the form of oxides, more particularly in the        highest oxidation state of the respective metals.        3. Chlorination of Iron and of the Further Metals    -   The oxidation products obtained above, especially based on        iron (III) oxide, and also the oxides of the further metals,        such as copper, zinc, lead and cobalt, and also silver, are        subjected to a chlorination, for which purpose solid or        pulverulent ammonium chloride (NH₄Cl) is added to the resulting        product mixture. The resultant mixture is heated to a        temperature of 300° C. At this temperature, iron(III) oxide is        converted to iron (III) chloride (FeCl₃), with release of        ammonia and water. The resulting gaseous ammonia is removed or        drawn off and used for the recycling of the chlorinating agent,        as described in section 6.).    -   The chlorination also results in the chlorides of the further        metals, especially copper chloride, zinc chloride, lead chloride        and cobalt chloride, and also, where appropriate, silver        chloride (at least in part).        4. Removal of Iron Chloride and of the Chlorides of the Further        Metals from the Product Mixture    -   For the selective sublimation of iron (III) chloride (FeCl₃),        the product mixture obtained after the chlorination is heated to        a temperature of 350° C., with iron (III) chloride being        transferred into the gas phase and being able to be taken off or        removed for corresponding further processing. Because of the        sublimation temperatures different from iron(III) chloride, the        chlorides of the further metals initially remain at least        substantially in the solid product mixture. Also remaining in        the product mixture are the corresponding noble metals, and also        silicon dioxide and calcium sulfate.    -   The chlorides of the further metals are subsequently removed        from the remaining product mixture by slurrying or dispersing of        the product mixture in water, with the chlorides of the further        metals (substantially with the exception of silver chloride)        going into solution in water, on account of their good        solubility properties, and in this way being removed or        isolated. The chlorides of the further metals, isolated in this        way, may be separated further, by means of selective        sedimentation or precipitation, or on the basis of        electrochemical or sorptive techniques, more particularly        adsorptive techniques, for example. In particular, from the        chlorides isolated in this way, it is also possible to obtain        the metals as such (by reduction, for example). In this way, in        particular, the metals copper, zinc, cobalt and lead are        removed, while the noble metals (gold and silver) remain in the        solid residue on account of their insolubility.    -   An analysis conducted for the remaining product mixture reveals        that on the basis of the procedure according to the invention,        the amount of iron and also of the further metals in the        remaining product mixture or residue can be reduced by more than        90%. This results equally in a concentration or enrichment of        the noble metal components, especially of gold and/or silver, in        the remaining product mixture. Hence, in relation to the        remaining product mixture, freed both from iron chloride and        from the chlorides of the metals, it is possible to find a gold        content of around 6 g/t and a silver content of around 30 g/t        (whereas the starting material contains about 2 g/t gold and 10        g/t silver).        5. Processing of Iron (III) Chloride (FeCl₃)    -   The iron chloride removed before by sublimation can be        desublimed, according to one first variant of the method of the        invention, with cooling, to give solid iron (III) chloride        (FeCl₃). The resulting iron (III) chloride (FeCl₃) has a very        high purity and can be marketed as a corresponding commercial        product.    -   According to a second variant of the method of the invention,        the sublimed iron(III) chloride may be subjected to reduction to        give metallic iron. For this purpose, iron (III) chloride        (FeCl₃) is reacted with a reducing agent in the form of hydrogen        in the gas phase at temperatures of 600° C. This results in        metallic iron and also hydrogen chloride. The resulting hydrogen        chloride is removed or taken off for the recycling of the        chlorinating agent, as described in section 6.).    -   The iron obtained on reduction is further analyzed by means of        x-ray fluorescence methods. The metallic iron obtained in the        manner described above has a purity of at least 99.9%. According        to this variant of the invention, therefore, high-purity        metallic iron is provided as a corresponding commercial product.        6. Recycling of the Chlorinating Agent    -   The gaseous ammonia resulting in the chlorination of iron oxide        or of the oxides of the further metals (cf. observations in        section 3.)) and drawn off is combined with the hydrogen        chloride resulting from the reduction of iron(III) chloride (cf.        observations in 5.)) and drawn off, and is reacted in the gas        phase, thereby producing recycled ammonium chloride (NH₄Cl),        which can be supplied again to the chlorinating operation in        accordance with section 3.).        7. Recovery of the Noble Metals    -   With regard to the remaining product mixture, present in solid        or insoluble form and freed from iron chloride and also from the        chlorides of the further metals, this mixture is subjected to a        further purification, particularly for the purpose of obtaining        the noble metals. Accordingly, the remaining product mixture,        which optionally is again slurried or dispersed, can be admixed        with cyanide liquor, thereby converting the noble metals present        in the product mixture into a water-soluble form, by means of a        complexation reaction. The remaining product mixture is removed        from this solution by filtration. The noble metal components, in        the form of gold and/or silver, can be obtained from the        solution by precipitation methods, using zinc dust or the like,        for example, to give purified or isolated gold and/or silver.        The yield of gold in this case, based on the starting material,        is at least 90%.        8. Recovery of Silicon and Calcium Sulfate    -   The remaining product mixture comprises silicon dioxide, which        can be subjected to reduction to give silicon, and also calcium        sulfate, which can be obtained in the same way.

On the basis of the method of the invention, extrapolated to 100 000 tof raw material in the form of roasted pyrites, as well as the noblemetals gold and silver, it is also possible to obtain about 50 000 t ofmetallic iron and also about 30 000 t of a mixture based on silicondioxide and calcium carbonate. With the method of the invention it ispossible in particular to provide commercial products both in the formof metallic iron and in the form of iron (III) chloride. Moreover, it ispossible to provide products based on the chlorides of the furthermetals, as indicated above, and/or the metals as such (in particular byreduction). The substances obtained are notable in particular for a highpurity. The method of the invention therefore permits an extensive and,moreover, selective processing of roasted pyrites. Not least on accountof the recycling of the chlorinating agent used in accordance with theinvention, the method of the invention displays a high overall economyand also improved environmental qualities.

LIST OF REFERENCE SYMBOLS

-   A Recovery plant-   1 Providing and/or processing device-   2 Oxidation and/or roasting device-   3 Chlorinating device-   4 Removing device-   5 Removing and/or filter device-   6 Comminuting means-   7 Drying means-   8 Supplying means of the chlorinating device-   9 Takeoff and/or removal means of the chlorinating device-   10 Reaction and/or condensation device-   11 Supplying means of the reaction and/or condensation device-   12 Further supplying means of the reaction and/or condensation    device-   13 Takeoff and/or removal means of the reaction and/or condensation    device-   14 Desublimation device-   15 Reduction device-   16 Supplying means of the reduction device-   17 Further supplying means of the reduction device-   18 Withdrawal and/or exporting means of the reduction device-   19 Supplying means of the desublimation device-   20 Slurrying and/or dispersing device-   21 Adding and/or supplying device-   22 Adding means of the adding and/or supplying device-   23 Extraction device-   24 Common device-   25 Means for iron chloride takeoff in the removing device-   26 Means for receiving a dissolving and/or suspending medium in the    slurrying and/or dispersing device-   27 Withdrawal means of the slurrying and/or dispersing device-   28 Means for receiving a precipitant in the extraction device

The invention claimed is:
 1. A method for obtaining at least one ofmetallic iron and iron chloride from ores or ore residues in the form ofpyrite residues, wherein the method comprises the following steps (a) to(d), wherein the below-indicated steps (a) to (d) are carried out in theorder listed hereinafter: (a) providing a starting material in the formof at least one ore or ore residue, wherein the starting materialcomprises: (i) iron, (ii) at least one noble metal selected from thegroup consisting of gold, silver, and combinations thereof, and also(iii) at least one further metal selected from the group consisting ofcopper, zinc, lead, cobalt, titanium, manganese, vanadium, chromium andcombinations thereof; (b) oxidation treatment comprising calcining andoxidative roasting of the starting material in the presence of at leastone oxidizing agent to form oxidation products including iron oxide andoxides of the further metals; (c) chlorination of the oxidation productsobtained in step (b) using at least one recyclable chlorinating agent,comprising the chlorination of iron oxide and oxides of the furthermetals to form a product mixture including iron chloride and chloridesof the further metals; (d) selectively removing of the iron chloridefrom the product mixture obtained in step (c) and subsequently removingof the chlorides of the further metals from the product mixture freedfrom iron chloride, wherein the selectively removing of iron chloridetakes place by sublimation of the iron chloride, wherein the ironchloride selectively removed in this way is obtained as such bysubsequent desublimation, or wherein, alternatively, the iron chlorideselectively removed is subjected to reduction to form metallic iron;wherein in step (c) the chlorination is carried out as a solid phasereaction and using ammonium chloride (NH₄CI) as chlorinating agent,wherein the ammonium chloride in step (c) is recycled by recovery ofammonia (NH₃) resulting from the chlorinating agent in the chlorinationof the oxidation products and subsequent reaction of the ammonia withhydrogen chloride (HCI) and wherein the recycling of the ammoniumchloride is carried out in a reaction- or condensation-device.
 2. Themethod as claimed in claim 1, wherein in step (a) or beforeimplementation of step (b), the starting material is comminuted andhomogenized.
 3. The method as claimed in claim 1, wherein in step (b)the oxidation treatment is carried out as a solid phase reaction and attemperatures in the range from 500° C. to 1000° C.
 4. The method asclaimed in claim 1, wherein, in the oxidation treatment in step (b),iron is substantially converted into iron(III) oxide.
 5. The method asclaimed in claim 1, wherein the oxidation products obtained in theoxidation treatment in step (b) comprises iron(III) oxide in amounts inthe range from 10 wt % to 95 wt %, based on the dry weight of theproduct mixture obtained in step (b).
 6. The method as claimed in claim1, wherein in step (c) iron oxide is reacted to form iron chloride. 7.The method as claimed in claim 1, wherein in step (d) the sublimation ofiron chloride from the product mixture obtained in step (c) takes placeat temperatures in the range from 200° C. to 400° C.
 8. The method asclaimed in claim 1, wherein step (c) and step (d) take place in a commondevice, wherein the common device comprises a first section forimplementing step (c) and a second section for implementing step (d). 9.The method as claimed in claim 8, wherein step (c) and step (d) takeplace in the common device continuously.
 10. The method as claimed inclaim 1, wherein in step (d) the desublimation leads to solid andpurified iron chloride being obtained.
 11. The method as claimed inclaim 1, wherein in step (d) the reduction of iron chloride takes placein the gas phase at temperatures in the range from 400° C. to 800° C.12. The method as claimed in claim 1, wherein the product mixture freedfrom iron chloride and obtained in step (d) comprises an iron content ofless than 10 wt %, calculated as element and based on the dry weight ofthe product mixture.
 13. The method as claimed in claim 1, wherein instep (d) a subsequent removing of chlorides of the further metals takesplace from the product mixture freed from iron chloride.
 14. The methodas claimed in claim 1, wherein the product mixture freed from ironchloride and obtained in step (d) and from the chlorides of the furthermetals comprises, calculated in each case as element and based in eachcase on the dry weight of the product mixture: gold in amounts in therange from 1 g/t to 50 g/t; silver in amounts in the range from 2 g/t to600 g/t.
 15. The method as claimed in claim 1, wherein, following step(d), a step (e) is carried out, wherein in step (e) the noble metal(s)is or are removed from the product mixture freed from iron chloride andobtained in step (d) and freed from the chlorides of the further metals.